Test "released" versions of AOSP LLVM?

[nathanchance]

We have no coverage of versions of AOSP LLVM that are being used for the released branches of Android, which could be a problem if stable takes a change that does not work with older but supported toolchains in those branches, as it would break downstream Android consumers.

My initial thought for supporting this is to ask TuxMake to support clang-android-11, clang-android-12, etc. to say use the Android clang version for Android 11, Android 12, etc. We can find those mappings in the build.config files in the various kernel/common branches.