diff --git a/scripts/ci/build_nim.sh b/scripts/ci/build_nim.sh
new file mode 100755
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--- /dev/null
+++ b/scripts/ci/build_nim.sh
@@ -0,0 +1,297 @@
+#!/usr/bin/env bash
+# used in Travis CI and AppVeyor scripts
+
+# Copyright (c) 2018-2020 Status Research & Development GmbH. Licensed under
+# either of:
+# - Apache License, version 2.0
+# - MIT license
+# at your option. This file may not be copied, modified, or distributed except
+# according to those terms.
+
+set -e
+
+# NIM_COMMIT could be a (partial) commit hash, a tag, a branch name, etc. Empty by default.
+NIM_COMMIT_HASH="" # full hash for NIM_COMMIT, retrieved in "nim_needs_rebuilding()"
+
+# script arguments
+[[ $# -ne 4 ]] && { echo "Usage: $0 nim_dir csources_dir nimble_dir ci_cache_dir"; exit 1; }
+NIM_DIR="$1"
+CSOURCES_DIR="$2" # can be relative to NIM_DIR; only used when `skipIntegrityCheck` unsupported
+NIMBLE_DIR="$3" # can be relative to NIM_DIR; only used when `skipIntegrityCheck` unsupported
+CI_CACHE="$4"
+
+## env vars
+# verbosity level
+[[ -z "$V" ]] && V=0
+[[ -z "$CC" ]] && CC="gcc"
+# to build csources in parallel, set MAKE="make -jN"
+[[ -z "$MAKE" ]] && MAKE="make"
+# for 32-bit binaries on a 64-bit host
+UCPU=""
+[[ "$ARCH_OVERRIDE" == "x86" ]] && UCPU="ucpu=i686"
+[[ -z "$NIM_BUILD_MSG" ]] && NIM_BUILD_MSG="Building the Nim compiler"
+[[ -z "$QUICK_AND_DIRTY_COMPILER" ]] && QUICK_AND_DIRTY_COMPILER=0
+[[ -z "$QUICK_AND_DIRTY_NIMBLE" ]] && QUICK_AND_DIRTY_NIMBLE=0
+
+# Windows detection
+if uname | grep -qiE "mingw|msys"; then
+	ON_WINDOWS=1
+	EXE_SUFFIX=".exe"
+	# otherwise it fails in AppVeyor due to https://github.com/git-for-windows/git/issues/2495
+	GIT_TIMESTAMP_ARG="--date=unix" # available since Git 2.9.4
+else
+	ON_WINDOWS=0
+	EXE_SUFFIX=""
+	GIT_TIMESTAMP_ARG="--date=format-local:%s" # available since Git 2.7.0
+fi
+
+NIM_BINARY="${NIM_DIR}/bin/nim${EXE_SUFFIX}"
+MAX_NIM_BINARIES="10" # Old ones get deleted.
+
+nim_needs_rebuilding() {
+	REBUILD=0
+	NO_REBUILD=1
+
+	if [[ ! -e "$NIM_DIR" ]]; then
+		# Shallow clone, optimised for the default NIM_COMMIT value.
+		git clone -q --depth=1 https://github.com/status-im/Nim.git "$NIM_DIR"
+	fi
+
+	pushd "${NIM_DIR}" >/dev/null
+	if [[ -n "${NIM_COMMIT}" ]]; then
+		# support old Git versions, like the one from Ubuntu-18.04
+		git restore . 2>/dev/null || git reset --hard
+		if ! git checkout -q ${NIM_COMMIT} 2>/dev/null; then
+			# Pay the price for a non-default NIM_COMMIT here, by fetching everything.
+			# (This includes upstream branches and tags that might be missing from our fork.)
+			git remote add upstream https://github.com/nim-lang/Nim
+			git fetch --all --tags --quiet
+			git checkout -q ${NIM_COMMIT}
+		fi
+		# In case the local branch diverged and a fast-forward merge is not possible.
+		git fetch || true
+		git reset -q --hard origin/${NIM_COMMIT} 2>/dev/null || true
+		# In case NIM_COMMIT is a local branch that's behind the remote one it's tracking.
+		git pull -q 2>/dev/null || true
+		git checkout -q ${NIM_COMMIT}
+		# We can't use "rev-parse" here, because it would return the tag object's
+		# hash instead of the commit hash, when NIM_COMMIT is a tag.
+		NIM_COMMIT_HASH="$(git rev-list -n 1 ${NIM_COMMIT})"
+	else
+		# NIM_COMMIT is empty, so assume the commit we need is already checked out
+		NIM_COMMIT_HASH="$(git rev-list -n 1 HEAD)"
+	fi
+	popd >/dev/null
+
+	if [[ -n "$CI_CACHE" && -d "$CI_CACHE" ]]; then
+		cp -a "$CI_CACHE"/* "$NIM_DIR"/bin/ || true # let this one fail with an empty cache dir
+	fi
+
+	# Delete old Nim binaries, to put a limit on how much storage we use.
+	for F in "$(ls -t "${NIM_DIR}"/bin/nim_commit_* 2>/dev/null | tail -n +$((MAX_NIM_BINARIES + 1)))"; do
+		if [[ -e "${F}" ]]; then
+			rm "${F}"
+		fi
+	done
+
+	# Compare the last built commit to the one requested.
+	# Handle the scenario where our symlink is manually deleted by the user.
+	if [[ -e "${NIM_DIR}/bin/last_built_commit" && \
+	-e "${NIM_DIR}/bin/nim${EXE_SUFFIX}" && \
+	"$(cat "${NIM_DIR}/bin/last_built_commit")" == "${NIM_COMMIT_HASH}" ]]; then
+		return $NO_REBUILD
+	elif [[ -e "${NIM_DIR}/bin/nim_commit_${NIM_COMMIT_HASH}" ]]; then
+		# we built the requested commit in the past, so we simply reuse it
+		rm -f "${NIM_DIR}/bin/nim${EXE_SUFFIX}"
+		ln -s "nim_commit_${NIM_COMMIT_HASH}" "${NIM_DIR}/bin/nim${EXE_SUFFIX}"
+		echo ${NIM_COMMIT_HASH} > "${NIM_DIR}/bin/last_built_commit"
+		return $NO_REBUILD
+	else
+		return $REBUILD
+	fi
+}
+
+build_nim() {
+	echo -e "$NIM_BUILD_MSG"
+	# [[ "$V" == "0" ]] && exec &>/dev/null
+
+	# working directory
+	pushd "$NIM_DIR"
+	if  grep -q "skipIntegrityCheck" koch.nim && [ "${NIM_COMMIT}" != "version-1-6" ]; then
+		echo "in if"
+		# Run Nim buildchain, with matching dependency versions
+		# - CSOURCES_REPO from Nim/config/build_config.txt (nim_csourcesUrl)
+		# - CSOURCES_COMMIT from Nim/config/build_config.txt (nim_csourcesHash)
+		# - NIMBLE_REPO from Nim/koch.nim (bundleNimbleExe)
+		# - NIMBLE_COMMIT from Nim/koch.nim (NimbleStableCommit)
+		. ci/funs.sh
+		NIMCORES=1 nimBuildCsourcesIfNeeded $UCPU
+		bin/nim c --noNimblePath --skipUserCfg --skipParentCfg --warnings:off --hints:off koch
+		./koch --skipIntegrityCheck boot -d:release --skipUserCfg --skipParentCfg --warnings:off --hints:off
+		if [[ "${QUICK_AND_DIRTY_COMPILER}" == "0" ]]; then
+			# We want tools
+			./koch tools -d:release --skipUserCfg --skipParentCfg --warnings:off --hints:off
+		elif [[ "${QUICK_AND_DIRTY_NIMBLE}" != "0" ]]; then
+			# We just want nimble
+			./koch nimble -d:release --skipUserCfg --skipParentCfg --warnings:off --hints:off
+		fi
+	else
+		# Git commits
+		echo "in else"
+
+		: ${CSOURCES_V1_COMMIT:=561b417c65791cd8356b5f73620914ceff845d10}
+		: ${CSOURCES_V2_COMMIT:=86742fb02c6606ab01a532a0085784effb2e753e}
+		: ${CSOURCES_V1_REPO:=https://github.com/nim-lang/csources_v1.git}
+		: ${CSOURCES_V2_REPO:=https://github.com/nim-lang/csources_v2.git}
+
+		# After this Nim commit, use csources v2
+		: ${CSOURCES_V2_START_COMMIT:=f7c203fb6c89b5cef83c4f326aeb23ef8c4a2c40}
+		: ${NIMBLE_REPO:=https://github.com/nim-lang/nimble.git}
+		: ${NIMBLE_COMMIT:=a4fc798838ee753f5485dd19afab22e9367eb0e7} # 0.13.1
+
+		# Custom buildchain for older versions
+		# TODO Remove this once the default NIM_COMMIT supports `--skipIntegrityCheck`
+		# We will still be able to compile older versions by removing the flag,
+		# which will just waste a bit of CPU
+
+		# Git repos for csources and Nimble
+		if [[ ! -d "$CSOURCES_DIR" ]]; then
+			if git merge-base --is-ancestor $CSOURCES_V2_START_COMMIT $NIM_COMMIT_HASH; then
+			  CSOURCES_REPO=$CSOURCES_V2_REPO
+			  CSOURCES_COMMIT=$CSOURCES_V2_COMMIT
+			else
+			  CSOURCES_REPO=$CSOURCES_V1_REPO
+			  CSOURCES_COMMIT=$CSOURCES_V1_COMMIT
+			fi
+
+			mkdir -p "$CSOURCES_DIR"
+			pushd "$CSOURCES_DIR"
+			git clone $CSOURCES_REPO .
+			git checkout $CSOURCES_COMMIT
+			popd
+		fi
+		if [[ "$CSOURCES_DIR" != "csources" ]]; then
+			rm -rf csources
+			ln -s "$CSOURCES_DIR" csources
+		fi
+
+		# bootstrap the Nim compiler and build the tools
+		rm -f bin/{nim,nim_csources}
+		pushd csources
+		if [[ "$ON_WINDOWS" == "0" ]]; then
+			$MAKE $UCPU clean
+			$MAKE $UCPU LD=$CC
+		else
+			$MAKE myos=windows $UCPU clean
+			$MAKE myos=windows $UCPU CC=gcc LD=gcc
+		fi
+		popd
+		if [[ -e csources/bin ]]; then
+			rm -f bin/nim bin/nim_csources
+			cp -a csources/bin/nim bin/nim
+			cp -a csources/bin/nim bin/nim_csources
+			rm -rf csources/bin
+		else
+			cp -a bin/nim bin/nim_csources
+		fi
+		if [[ "$QUICK_AND_DIRTY_COMPILER" == "0" ]]; then
+			sed \
+				-e 's/koch$/--warnings:off --hints:off koch/' \
+				-e 's/koch boot/koch boot --warnings:off --hints:off/' \
+				-e '/nimBuildCsourcesIfNeeded/d' \
+				build_all.sh > build_all_custom.sh
+			sh build_all_custom.sh
+			rm build_all_custom.sh
+		else
+			# Don't re-build it multiple times until we get identical
+			# binaries, like "build_all.sh" does. Don't build any tools
+			# either. This is all about build speed, not developer comfort.
+			bin/nim_csources \
+				c \
+				--compileOnly \
+				--nimcache:nimcache \
+				-d:release \
+				--skipUserCfg \
+				--skipParentCfg \
+				--warnings:off \
+				--hints:off \
+				compiler/nim.nim
+			bin/nim_csources \
+				jsonscript \
+				--nimcache:nimcache \
+				--skipUserCfg \
+				--skipParentCfg \
+				compiler/nim.nim
+			cp -a compiler/nim bin/nim1
+			# If we stop here, we risk ending up with a buggy compiler:
+			# https://github.com/status-im/nimbus-eth2/pull/2220
+			# https://github.com/status-im/nimbus-eth2/issues/2310
+			bin/nim1 \
+				c \
+				--compileOnly \
+				--nimcache:nimcache \
+				-d:release \
+				--skipUserCfg \
+				--skipParentCfg \
+				--warnings:off \
+				--hints:off \
+				compiler/nim.nim
+			bin/nim1 \
+				jsonscript \
+				--nimcache:nimcache \
+				--skipUserCfg \
+				--skipParentCfg \
+				compiler/nim.nim
+			rm -f bin/nim
+			cp -a compiler/nim bin/nim
+			rm bin/nim1
+
+			if [[ ! -d "$NIMBLE_DIR" ]]; then
+				mkdir -p "$NIMBLE_DIR"
+				pushd "$NIMBLE_DIR"
+				git clone $NIMBLE_REPO .
+				git checkout $NIMBLE_COMMIT
+				pwd
+				../../bin/nim r src/nimblepkg/private/clone.nim
+				# we have to delete .git or koch.nim will checkout a branch tip, overriding our target commit
+				rm -rf .git
+				popd
+			fi
+			if [[ "$NIMBLE_DIR" != "dist/nimble" ]]; then
+				mkdir -p dist
+				rm -rf dist/nimble
+				ln -s ../"$NIMBLE_DIR" dist/nimble
+			fi
+			# Do we want Nimble in this quick build?
+			if [[ "${QUICK_AND_DIRTY_NIMBLE}" != "0" ]]; then
+				bin/nim c -d:release --noNimblePath --skipUserCfg --skipParentCfg dist/nimble/src/nimble.nim
+				mv dist/nimble/src/nimble bin/
+        	fi
+        fi
+	fi
+
+	if [[ "$QUICK_AND_DIRTY_COMPILER" == "0" || "${QUICK_AND_DIRTY_NIMBLE}" != "0" ]]; then
+		# Nimble needs a CA cert
+		rm -f bin/cacert.pem
+		curl -LsS -o bin/cacert.pem https://curl.se/ca/cacert.pem || echo "Warning: 'curl' failed to download a CA cert needed by Nimble. Ignoring it."
+	fi
+
+	# record the built commit
+	echo ${NIM_COMMIT_HASH} > bin/last_built_commit
+
+	# create the symlink
+	mv bin/nim bin/nim_commit_${NIM_COMMIT_HASH}
+	ln -s nim_commit_${NIM_COMMIT_HASH} bin/nim${EXE_SUFFIX}
+
+	# update the CI cache
+	popd # we were in $NIM_DIR
+	if [[ -n "$CI_CACHE" ]]; then
+		rm -rf "$CI_CACHE"
+		mkdir "$CI_CACHE"
+		cp "$NIM_DIR"/bin/* "$CI_CACHE"/
+	fi
+}
+
+if nim_needs_rebuilding; then
+	build_nim
+fi