uucore, uptime: various deprecation warnings with musl

[cakebaker]

In the CI, various deprecation warnings show up in musl-related jobs (I omitted duplicate warnings):

warning: use of deprecated type alias `libc::time_t`: This type is changed to 64-bit in musl 1.2.0, we'll follow that change in the future release. See #1848 for more info.
  --> src/uucore/src/lib/features/uptime.rs:17:11
   |
17 | use libc::time_t;
   |           ^^^^^^
   |
   = note: `#[warn(deprecated)]` on by default

warning: use of deprecated function `libc::endutxent`: musl provides `utmp` as stubs and an alternative should be preferred; see https://wiki.musl-libc.org/faq.html
  --> src/uucore/src/lib/features/utmpx.rs:43:15
   |
43 | pub use libc::endutxent;
   |               ^^^^^^^^^

warning: use of deprecated function `libc::getutxent`: musl provides `utmp` as stubs and an alternative should be preferred; see https://wiki.musl-libc.org/faq.html
  --> src/uucore/src/lib/features/utmpx.rs:44:15
   |
44 | pub use libc::getutxent;
   |               ^^^^^^^^^

warning: use of deprecated function `libc::setutxent`: musl provides `utmp` as stubs and an alternative should be preferred; see https://wiki.musl-libc.org/faq.html
  --> src/uucore/src/lib/features/utmpx.rs:45:15
   |
45 | pub use libc::setutxent;
   |               ^^^^^^^^^

warning: use of deprecated function `libc::utmpxname`: musl provides `utmp` as stubs and an alternative should be preferred; see https://wiki.musl-libc.org/faq.html
  --> src/uucore/src/lib/features/utmpx.rs:48:15
   |
48 | pub use libc::utmpxname;
   |               ^^^^^^^^^

[sylvestre]

@Ecordonnier FYI in case you would like to fix them

[Ecordonnier]

I would say this is expected behavior. I added those warnings in the libc create to warn that those functions are only stubs (see also . #7740 (comment) ). However calling those stubs from uutils-coreutils makes sense in order to have identical behavior with GNU coreutils and avoid special logic for musl libc. What would you like to change?

I can silence the warnings if you want (on the other side I think those warnings are useful for developers working with musl). There is no alternative function that musl offers which can be used.