[compiler-rt] [sanitizer_common] Drop remaining support for Android 5 or older (PR #146187)

[via llvm-commits]

https://github.com/enh-google approved this pull request.

good news! api levels this old were already not supported in the ndk anyway (and, funnily enough, _new_ api levels only support hwasan too): https://developer.android.com/ndk/guides/asan

https://github.com/llvm/llvm-project/pull/146187