Install clang to run adress sanitizer

The address sanitizer job is silently failing at the moment because we
do not install clang.

Install clang so the address sanitizer job can run. Do not fix the
silent failure, that will be done later on.

Author: tcharding

.github/workflows/rust.yml

@@ -9,6 +9,8 @@ jobs:
     steps:
       - name: Checkout Crate
         uses: actions/checkout@v2
+      - name: Install clang     # Needed for ASan.
+        run: sudo apt-get -y clang-9
       - name: Checkout Toolchain
         uses: actions-rs/toolchain@v1
         with: