libcrypt was no longer built by default since glibc-2.38, and it has been
completely removed since glibc-2.39.
Let's always use libxcrypt, unless when building with musl. As already
major distribution already have libxcrypt-4.4.x, hence let's also bump
the required minimum version to 4.4.0.
libxcrypt cannot be built with musl, hence the previous fallback logic
in libcrypt-util.c are moved to musl/crypt.c.
Note, libxcrypt-4.4.0 was released on 2018-11-20.
See also #38608.
musl's getopt_long() behaves something different in handling optional arguments:
```
$ journalctl _PID=1 _COMM=systemd --since 19:19:01 -n all --follow
Failed to add match 'all': Invalid argument
```
This introduces getopt_long_fix() that reorders the passed arguments to make
getopt_long() provided by musl works as what we expect.
Also, musl's getopt() always behaves POSIXLY_CORRECT mode, and stops parsing
arguments when a non-option string found. Let's always use getopt_long().
musl provides XSI compliant strerror_r(), and it is slightly different
from the one by glibc.
Let's introduce a tiny wrapper to convert XSI strerror_r() to GNU one.
The wrapper also patches musl's spurious catchall error message.
Then, move syscall definitions to the wrapper, and prototypes are moved
to relevant headers.
This also adds checks for add_key() and request_key(), as one day
glibc may be going to add some of them separatedly.
The check for fspick in meson.build is dropped, as it is currently
unused in our code.
This also moves
- basic/missing_bpf.h -> include/override/linux/bpf.h,
- basic/missing_keyctl.h -> include/override/linux/keyctl.h.
Yu Watanabe
Emil Renner BerthingandYu Watanabe