run single-threaded to ease debugging

Author: ulysses4ever

.github/workflows/validate.yml

@@ -27,7 +27,7 @@ env:
   # Ideally we should use the version about to be released for hackage tests and benchmarks
   GHC_FOR_SOLVER_BENCHMARKS: '9.2.3'
   GHC_FOR_COMPLETE_HACKAGE_TESTS: '9.2.3'
-  COMMON_FLAGS: '-j 2 -v'
+  COMMON_FLAGS: '-v'
 
 jobs:
   validate-prerelease: