add llvm to github action container

Signed-off-by: josantos <josantos@amd.com>

.github/workflows/ubuntu-focal.yml

@@ -30,6 +30,7 @@ jobs:
           sudo apt-get install -y git
           sudo apt-get install -y python3-pip
           sudo apt-get install -y cmake
+          sudo apt-get install llvm-7
       - name: Checkout
         uses: actions/checkout@v3
       - name: Install Python prereqs