Increase build parallelism on macOS (#2759)

Co-authored-by: Martin Hořeňovský <[email protected]>

Author: kkarbowiak

.github/workflows/mac-builds.yml

@@ -42,11 +42,10 @@ jobs:
 
     - name: Build tests + lib
       working-directory: ${{runner.workspace}}/build
-      run: make -j 2
+      run: make -j `sysctl -n hw.ncpu`
 
     - name: Run tests
       env:
           CTEST_OUTPUT_ON_FAILURE: 1
       working-directory: ${{runner.workspace}}/build
-      # Hardcode 2 cores we know are there
-      run: ctest -C ${{matrix.build_type}} -j 2
+      run: ctest -C ${{matrix.build_type}} -j `sysctl -n hw.ncpu`