Skip CI job ubuntu-parallel on forks (#766)

* Skip job for forks.
* Minor formatting. (`--oversubscribe` is identical to `-oversubscribe`, but `--oversubscribe` is more common)

---------

Co-authored-by: Markus Mützel <markus.muetzel@gmx.de>

Author: BenjaminRodenberg

.github/workflows/ubuntu-parallel.yaml

@@ -14,8 +14,9 @@ on:
 jobs:
 
   ubuntu:
+    if: ${{ github.repository == 'ElmerCSC/elmerfem' }}  # only run job for main repository (forks usually do not have self-hosted runners)
     runs-on: self-hosted
-    
+
     name: ubuntu-parallel (${{ matrix.compiler }})
 
     strategy:

flake.nix

@@ -104,7 +104,7 @@
 
                 "-DWITH_ElmerIce:BOOL=TRUE"
 
-                "-DMPIEXEC_PREFLAGS=-oversubscribe"
+                "-DMPIEXEC_PREFLAGS=--oversubscribe"
 
                 "-Wno-dev"
               ]