clang 8 included in actions env (#2670)

* ensure we use clang-format-8

.github/workflows/tests.yml

@@ -27,12 +27,7 @@ jobs:
       - name: Get clang-format 8
         env: 
           DEBIAN_FRONTEND: noninteractive
-        run: |
-          APT_KEY_DONT_WARN_ON_DANGEROUS_USAGE=1 wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key|sudo apt-key add - 
-          sudo add-apt-repository 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-8 main' -y
-          sudo apt update -y
-          sudo apt install -y clang-format-8
-          sudo ln -s /usr/bin/clang-format-8 /usr/bin/clang-format
+        run: sudo update-alternatives --install /usr/bin/clang-format clang-format /usr/bin/clang-format-8 1000
       - name: Clang Format
         run: ci/check-commit-format.sh