[ci] add llvm ppa

Author: JSUYA

.github/workflows/build.yml

@@ -30,8 +30,9 @@ jobs:
 
       - name: Install dependencies
         run: |
+          sudo bash -c "$(wget -O - https://apt.llvm.org/llvm.sh)" -- 12
           sudo apt-get update
-          sudo apt-get install -y clang-12 rpm2cpio cpio binutils-${{ matrix.triple }}
+          sudo apt-get install -y rpm2cpio cpio binutils-${{ matrix.triple }}
 
       - name: Install depot_tools
         run: |