This patch was inspired by Adhemerval Zanella’s proposed glibc patches:
https://sourceware.org/pipermail/libc-alpha/2020-August/117294.html
The idea is to make it easier for Gnulib lib/getcwd.c to match
glibc io/getcwd-generic.c.
* lib/getcwd.c [_LIBC]: Do not include pathmax.h.
Include not-cancel.h.
(HAVE_OPENAT, D_INO_IN_DIRENT, HAVE_MSVC_INVALID_PARAMETER_HANDLER)
(HAVE_MINIMALLY_WORKING_GETCWD): Define for the _LIBC case.
(__getcwd, __lstat, __readdir) [!_LIBC]: Remove these macros.
(__close_nocancel_nostatus, __getcwd_generic, stat64, __fstat64)
(__fstatat64, __lstat64, __readdir64, __fdopendir, __openat)
(__rewinddir, __openat64, dirent64) [_LIBC]: New macros.
(__getcwd_generic): Rename from __getcwd.
Use the abovementioned macros for consistency with glibc.
(weak_alias): Remove.