Update cmake-multi-platform.yml

Author: TimGoTheCreator

.github/workflows/cmake-multi-platform.yml

@@ -55,6 +55,9 @@ jobs:
       shell: bash
       run: |
         echo "build-output-dir=${{ github.workspace }}/build" >> "$GITHUB_OUTPUT"
+     - name: Install OpenMP (Ubuntu) 
+       if matrix.os == 'ubuntu.latest'
+       run: sudo apt-get update && sudo apt-get install -y libomp-dev 
 
     - name: Configure CMake
       # Configure CMake in a 'build' subdirectory. `CMAKE_BUILD_TYPE` is only required if you are using a single-configuration generator such as make.