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

[Alex Fan via cfe-commits]

alexfanqi wrote:

Sorry. It took some time to reply. Since newer linux kernel supports sv57 and sv48, I tested this again with latest qemu and 6.6 kernel, by passing `-cpu rv64,sv48=on` to qemu.

I missed a little piece here for sv48,

Also to note, if we want to support sv57, we could directly copy the aarch64_48 scheme and append 8 bits to its addresses. That gives the maximum application space, a horrific ~2^24 tera byte.

I asked @hiraditya to land for me. Thanks for the help to drive the reland.

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