[compiler-rt] [compiler-rt][asan] Fix for flaky asan check (PR #88177)

[via llvm-commits]

PiJoules wrote:

> On https://reviews.llvm.org/D158786 I didn't realized that it's not thread safe, it should be easy to make `LowLevelAllocator` thread safe.
> 
> Feel free just to add TODO, or we can do thread safe in this patch?
> 
> This is approx idea how this could be done https://github.com/llvm/llvm-project/blob/6bf71be9f920417a772b123fd42ab855496ad149/compiler-rt/lib/sanitizer_common/sanitizer_stack_store.cpp

Added just the TODO for now since we know this quick fix works but I'll followup with the threadsafe changes afterwards. Just want to make sure the libc tests this might affect for us downstream absorb this change well.

https://github.com/llvm/llvm-project/pull/88177