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

[Fangrui Song via llvm-commits]

MaskRay wrote:

> Without this patch, use-of-uninitialized value will occur on those architectures, which are supported by Glibc since version 2.33. Because they have no opportunity to implement the __fxstat{,64} interfaces.

"those architectures" are not clear. I assume it includes LoongArch (base version 2.36) and some RISC-V variants (`sysdeps/unix/sysv/linux/riscv/shlib-versions`)

This description needs rewording. I think there may be a difference if a glibc port has a base version >= 2.33. https://maskray.me/blog/2022-05-29-glibc#buildabi-versions.h

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