sadd CC_CMD to GITHUB_ENV to build Nim compiler

.github/actions/install_nim/action.yml

@@ -30,12 +30,14 @@ runs:
 
         ncpu=
         MAKE_CMD="make"
+        CC_CMD="gcc"
         case '${{ inputs.os }}' in
         'Linux')
           ncpu=$(nproc)
           ;;
         'macOS')
           ncpu=$(sysctl -n hw.ncpu)
+          CC_CMD="clang"
           ;;
         'Windows')
           ncpu=$NUMBER_OF_PROCESSORS
@@ -45,6 +47,7 @@ runs:
         [[ -z "$ncpu" || $ncpu -le 0 ]] && ncpu=1
         echo "ncpu=$ncpu" >> $GITHUB_ENV
         echo "MAKE_CMD=${MAKE_CMD}" >> $GITHUB_ENV
+        echo "CC_CMD=${CC_CMD}" >> $GITHUB_ENV
         echo '${{ github.workspace }}/nim/bin' >> $GITHUB_PATH
 
     - name: Restore Nim from cache
@@ -61,7 +64,7 @@ runs:
         rm -rf nim
         curl -O -L -s -S https://raw.githubusercontent.com/status-im/nimbus-build-system/master/scripts/build_nim.sh
         env MAKE="${MAKE_CMD} -j${ncpu}" ARCH_OVERRIDE=${PLATFORM} NIM_COMMIT=${{ inputs.nim_ref }} \
-          QUICK_AND_DIRTY_COMPILER=1 QUICK_AND_DIRTY_NIMBLE=1 CC=gcc \
+          QUICK_AND_DIRTY_COMPILER=1 QUICK_AND_DIRTY_NIMBLE=1 CC=${CC_CMD} \
           bash build_nim.sh nim csources dist/nimble NimBinaries
 
     - name: Install Nimble (pinned)