[compiler-rt] [tsan] Refine fstat{, 64} interceptors on GLIBC (PR #85612)

[via llvm-commits]

wangleiat wrote:

> use-of-uninitialized is MSAN, but the patch is TSAN only?

I apologize for my inadequate English description causing inconvenience. My intention was that on systems where __fxstat{,64} is not implemented, interception would result in calling an empty function.

https://github.com/llvm/llvm-project/pull/85612