[clang] [TSAN] add support for riscv64 (PR #68735)

[via cfe-commits]

hiraditya wrote:

> The review context is on https://reviews.llvm.org/D145214 . Moving it here just causes more confusion.
> 
> @alexfanqi is the author of the patch and they can drive a reland.

Can you elaborate what is confusing? The patch was already reviewed and accepted. I'm waiting on the author to reply back but I posted here for it to be tested. @alexfanqi asked me to land the patch last time (https://reviews.llvm.org/D145214#4650928)

https://github.com/llvm/llvm-project/pull/68735