move `-d:nimRawSetjmp` to config.nim

Refs https://github.com/status-im/nimbus-build-system/issues/44

.github/workflows/ci.yml

@@ -149,10 +149,6 @@ jobs:
 
       - name: Run tests
         run: |
-          if [[ "${{ matrix.target.os }}" == "windows" ]]; then
-            # https://github.com/status-im/nimbus-eth2/issues/3121
-            export NIMFLAGS="-d:nimRawSetjmp"
-          fi
           nim --version
           nimble --version
           env TEST_LANG=c nimble test

config.nims

@@ -0,0 +1,4 @@
+if defined(windows):
+  # Avoid some rare stack corruption while using exceptions with a SEH-enabled
+  # toolchain: https://github.com/status-im/nimbus-eth2/issues/3121
+  switch("define", "nimRawSetjmp")

tests/config.nims

@@ -0,0 +1,4 @@
+if defined(windows):
+  # Avoid some rare stack corruption while using exceptions with a SEH-enabled
+  # toolchain: https://github.com/status-im/nimbus-eth2/issues/3121
+  switch("define", "nimRawSetjmp")