These are unneeded even on AIX, PURE_WINDOWS, and ZOS (per #104706)
* HAVE_ERRNO_H: introduced by 1a93330ffa2ae2aa0b49461f05e6f0d51e8443f8 (2009) but unneeded.
The guarded ABI is unconditionally used by lldb.
* HAVE_FCNTL_H
* HAVE_FENV_H
* HAVE_SYS_STAT_H
Pull Request: https://github.com/llvm/llvm-project/pull/123087