Try https for llvm apt?

Author: baldurk

.github/workflows/ci.yml

@@ -328,8 +328,8 @@ jobs:
         fetch-depth: 5
     - name: Add LLVM apt repository
       run: |
-        wget -O - http://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
-        sudo add-apt-repository -y 'deb http://apt.llvm.org/xenial/ llvm-toolchain-xenial-3.8 main'
+        wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
+        sudo add-apt-repository -y 'deb https://apt.llvm.org/xenial/ llvm-toolchain-xenial-3.8 main'
         sudo apt-get update
         curl -LO http://archive.ubuntu.com/ubuntu/pool/main/libf/libffi/libffi6_3.2.1-8_amd64.deb
         curl -LO http://archive.ubuntu.com/ubuntu/pool/main/g/gcc-5/libubsan0_5.4.0-6ubuntu1~16.04.12_amd64.deb