GRIDEDIT-1926 install OpenMP

Author: ScottWillcox

.github/workflows/build-and-test-workflow.yml

@@ -43,6 +43,16 @@ jobs:
           elif [ "${{ runner.os }}" == "Linux" ]; then
             sudo apt-get install libboost-all-dev doxygen
           fi
+      
+      # Step: Install OpenMP
+      - name: Install OpenMP
+        run: brew install libomp
+
+      # Step: Set OpenMP environment variables
+      - name: Set OpenMP environment variables
+        run: |
+          echo "LDFLAGS=-L/opt/homebrew/opt/libomp/lib" >> $GITHUB_ENV
+          echo "CPPFLAGS=-I/opt/homebrew/opt/libomp/include" >> $GITHUB_ENV
 
       # Step: Restore cached user-provided dependencies
       - name: Restore cached user-provided dependencies
@@ -92,6 +102,9 @@ jobs:
           -DCMAKE_BUILD_TYPE=${{ inputs.build_type }}
           -DCMAKE_PREFIX_PATH=${{ steps.paths.outputs.ext_deps_dir }}/netcdf-c/install/netcdf-c
           -DCMAKE_INSTALL_PREFIX=${{ steps.paths.outputs.install_dir }}
+          -DCMAKE_C_FLAGS="-Xpreprocessor -fopenmp -I/opt/homebrew/opt/libomp/include"
+          -DCMAKE_CXX_FLAGS="-Xpreprocessor -fopenmp -I/opt/homebrew/opt/libomp/include"
+          -DCMAKE_EXE_LINKER_FLAGS="-L/opt/homebrew/opt/libomp/lib -lomp"
 
       # Step: CMake build
       - name: Build