printenv skips environment variables with invalid UTF-8

[sylvestre]

closes: #9701

[github-actions]

GNU testsuite comparison:

Congrats! The gnu test tests/tail/inotify-dir-recreate is now passing!

[github-actions]

GNU testsuite comparison:

Congrats! The gnu test tests/misc/nohup is no longer failing!
Note: The gnu test tests/tail/inotify-dir-recreate is now being skipped but was previously passing.

[github-actions]

GNU testsuite comparison:

Congrats! The gnu test tests/tail/inotify-dir-recreate is now passing!

[github-actions]

GNU testsuite comparison:

Note: The gnu test tests/tail/inotify-dir-recreate is now being skipped but was previously passing.

[cakebaker]

I would move the imports to the test function, otherwise there are "unused import" warnings on Android and the BSDs.

[ChrisDryden]

I was thinking that for most of the code we can use a helper function like this:

  fn write_os_str(out: &mut impl Write, s: &OsStr) -> io::Result<()> {
      #[cfg(unix)]
      {
          use std::os::unix::ffi::OsStrExt;
          out.write_all(s.as_bytes())
      }
      #[cfg(not(unix))]
      {
          // On Windows, OsString to_string_lossy is lossless
          out.write_all(s.to_string_lossy().as_bytes())
      }
  }

So everything can be kept as OsString, then in all of the functions they have the same code path without having the inline cfg stuff. Would be good to have most of our code move away from String by default through this too

[ChrisDryden]

Hey this helper function actually already exists in: write_all_os

coreutils/src/uucore/src/lib/mods/display.rs

Line 115 in 16f7350

fn write_all_os(&mut self, buf: &OsStr) -> io::Result<()> {

[ChrisDryden]

To make an example of how it could be used here I made a PR doing the similar thing for the env command: #9144

Makes the implementation way smaller compared to the inlining

[asder8215]

I think you accidentally referenced the wc PR, think you meant this #9726?