AIX: dlopen flags for RTLD_MEMBER and RTLD_NOAUTODEFER

[mustartt]

On AIX, we can dlopen an ar archive directly with RTLD_MEMBER flag.
https://www.ibm.com/docs/en/aix/7.3?topic=d-dlopen-subroutine

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

[rustbot]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @tgross35 (or someone else) some time within the next two weeks.

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[tgross35]

LGTM, CI doesn't pass with the latest nightly so I'll merge it tomorrow.

[mustartt]

Thanks for taking a look. Is this a good candidate for libc-0.2? It would be nice to have this in rustc relatively soon

[tgross35]

Indeed, just forgot to label

@rustbot label +stable-nominated