[libcxx-commits] [libcxx] [libcxx] Fix build for glibc < 2.27 (PR #121893)

[Jannik Glückert via libcxx-commits]

Jannik2099 wrote:

> In that case, this patch LGTM

no, see AIX CI

```
/scratch/powerllvm/cpap8006/llvm-project/libcxx-ci/libcxx/src/filesystem/operations.cpp:43:29: error: function-like macro '_LIBCPP_GLIBC_PREREQ' is not defined
   43 | #if (defined(__linux__) && (_LIBCPP_GLIBC_PREREQ(2, 27) || _LIBCPP_HAS_MUSL_LIBC)) || defined(__FreeBSD__)
      |                             ^
1 error generated.
```

this'll require a bit of ugly `#if defined()` machinery, unless we just define `_LIBCPP_GLIBC_PREREQ` to 0 on non-glibc?

https://github.com/llvm/llvm-project/pull/121893