Use unique errno values for AIX

[xingxue-ibm]

Description

AIX defines some errno values as aliases of other errno values under the _ALL_SOURCE macro, but the POSIX standard requires each errno to be unique. This also causes some crates, such as nix, to fail. This PR updates the affected errno values in libc to address the issue.

Sources

Checklist

• Relevant tests in libc-test/semver have been updated
• No placeholder or unstable values like *LAST or *MAX are
  included (see #3131)
• Tested locally (cd libc-test && cargo test --target mytarget);
  especially relevant for platforms that may not be checked in CI

[collinfunk]

Can confirm this is the case on an AIX 7.3 machine I have access to. EWOULDBLOCK == EAGAIN if _XOPEN_SOURCE_EXTENDED == 1 and ENOTEMPTY == EEXIST if defined _ALL_SOURCE. I'm assuming that _ALL_SOURCE will define _XOPEN_SOURCE_EXTENDED to 1, much like other feature macros.

Therefore, this change looks good to me.

[tgross35]

Thanks @xingxue-ibm for the PR and @collinfunk for reviewing!

I'm assuming you want this in 0.2 so

@rustbot label +stable-nominated

[xingxue-ibm]

Thanks so much, @collinfunk and @tgross35! Yes, it will be great if the fix can be included in the stable branch.