[compiler-rt] Allow libsanitizer to work on qemu-alpha (PR #201861)

[Thurston Dang via llvm-commits]

https://github.com/thurstond approved this pull request.

Thanks, LGTM!

Nit: I suggest renaming the title to something like "[ASan] Improve qemu-alpha shadow mapping" (libsanitizer is a downstream fork and encompasses multiple sanitizers; shadow mapping is the specific fix).

https://github.com/llvm/llvm-project/pull/201861