move -d:nimRawSetjmp to nim.cfg (#14)

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

.github/workflows/ci.yml

@@ -155,10 +155,6 @@ 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
           env TEST_LANG="c" nim --hints:off --verbosity:0 test
           env TEST_LANG="cpp" nim --hints:off --verbosity:0 test

nim.cfg

@@ -6,3 +6,8 @@
 
 --threads:on
 
+# Avoid some rare stack corruption while using exceptions with a SEH-enabled
+# toolchain: https://github.com/status-im/nimbus-eth2/issues/3121
+@if windows and not vcc:
+  --define:nimRawSetjmp
+@end