ci: Use Ubuntu 22.04 to ensure compatibility with older LLVM versions

GitHub Actions is migrating ubuntu-latest to Ubuntu 24.04, which no
longer provides the libtinfo5 package. Since older LLVM versions depend
on libtinfo5 and do not offer pre-built binaries for recent Ubuntu versions,
we explicitly specify ubuntu-22.04 in the workflow to maintain compatibility.

.github/workflows/main.yml

@@ -12,15 +12,15 @@ jobs:
         # use different LLVM versions among oses because of the lack of
         # official assets on github.
         include:
-          - os: ubuntu-latest
+          - os: ubuntu-22.04
             clang_version: 10.0.0
             llvm_asset_suffix: x86_64-linux-gnu-ubuntu-18.04
           - os: macos-latest
             clang_version: 10.0.0
             llvm_asset_suffix: x86_64-apple-darwin
           - os: windows-latest
             clang_version: 10.0.0
-          - os: ubuntu-latest
+          - os: ubuntu-22.04
             clang_version: 16.0.0
             llvm_asset_suffix: x86_64-linux-gnu-ubuntu-18.04
             enable_pic: true