Fix CI: use absolute path for case.py in mfc run test

The mfc wrapper creates its own temporary directory and changes into it,
so relative paths like 'case.py' don't work. Use absolute path instead.

Author: sbryngelson

.github/workflows/homebrew.yml

@@ -151,8 +151,8 @@ jobs:
           cp $(brew --prefix mfc)/examples/1D_sodshocktube/case.py "$TESTDIR/"
           
           echo "Running with $(sysctl -n hw.ncpu) processors..."
-          cd "$TESTDIR"
-          mfc run case.py -j $(sysctl -n hw.ncpu)
+          # Use absolute path since mfc wrapper creates its own tmpdir
+          mfc run "$TESTDIR/case.py" -j $(sysctl -n hw.ncpu)
           
           echo "Test case completed successfully!"