Tentatively merge https://github.com/llvm/llvm-project/pull/77242

Tentatively merge https://github.com/llvm/llvm-project/pull/77242

  [libcxx] Re-include <osreldate.h> in __config for FreeBSD

  In 0a97720d0197 some changes were made to `__config` for assuming that
  `__BYTE_ORDER__` is always present.

  However, this deleted a `<osreldate.h>` include for FreeBSD, which is
  required to get the value of `__FreeBSD_version`, and that is used later
  in the file to determine whether `_LIBCPP_C_HAS_NO_GETS` needs to be
  enabled.

  Include `<osreldate.h>` just after the other includes used for feature
  detection, to fix this.

  Note that when FreeBSD 13 is EOLed, this can be removed, as then all
  supported FreeBSD versions will no longer have `gets()`.

PR:		276104
MFC after:	1 month