Force mapping by core on Github

Author: weslleyspereira

.github/workflows/cmake.yml

@@ -24,7 +24,7 @@ env:
   CFLAGS: "-Wall -pedantic"
   FFLAGS: "-fcheck=all,no-bounds"
   BUILD_TYPE: Release
-  MPIEXEC_PREFLAGS: "--oversubscribe"
+  MPIEXEC_PREFLAGS: "--oversubscribe --map-by core"
 
 defaults:
   run: