Add group calls to android

[Takashiidobe]

Following #3014, this PR just implements the group side of the calls, since that doesn't require CI to be updated.

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[JohnTitor]

@bors r+

[bors]

📌 Commit 533b8cc has been approved by JohnTitor

It is now in the queue for this repository.

[bors]

⌛ Testing commit 533b8cc with merge e794d17...

[bors]

💔 Test failed - checks-actions

[Takashiidobe]

I'll reopen this when the android CI gets fixed up.

[Takashiidobe]

perfect, looks like I get this error message on arm-linux-androideabi, time to fix it up

stderr ---
WARNING: linker: /data/local/tmp/main-418f900fe48d7afe: unsupported flags DT_FLAGS_1=0x8000001
CANNOT LINK EXECUTABLE "/data/local/tmp/main-418f900fe48d7afe": cannot locate symbol "setgrent" referenced by "/data/local/tmp/main-418f900fe48d7afe"...

[tgross35]

@Takashiidobe would you be able to rebase? I can help figure out the problems if they still exist.

[Takashiidobe]

Still get the same error message, and I think I remember why.

CI is on API 24 which is before these calls were introduced (API 26) so this PR won't pass.

Just to sanity check, I ran it on my phone which is on API 31, and writing a small program to call getgrent works.

I'm not sure if there's a requirement on API level being capped at 24 (if so, then this PR shouldn't pass until that's changed) or if that's a CI limitation?

[tgross35]

You should just be able to exclude tests for the relevant functions in libc-test/build.rs the test_android function.

Cc @maurer (android change)

[tgross35]

LGTM but I'll wait for maurer to take a look. Please squash & rebase.

[maurer]

This is fine/appropriate to put into libc in case it's needed for compatibility.

To @Takashiidobe - these functions are performance footguns - Android has too many AIDs, so iterating through them in this fashion can take a nontrivial amount of time, ID based functions are preferred. Iterating via getgrent may take up to an eighth of a second to get through everything. They were primarily added for compatibility and tests.