Enable strftime, mkostemp[s] on Redox

[joshuamegnauth54]

Description

I exported a few functions that Redox's relibc supports (see the sources section). Nothing fancy.

Sources

Here are links to where the functions are implemented in relibc:

• mkostemp
• mkostemps
• strftime

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

[tgross35]

This LGTM, thanks for providing links. Any reason it's marked as a draft?

[joshuamegnauth54]

I wanted to get confirmation from someone from Redox first. Also, I didn't run the tests yet due to a busy day (I hope to run them soon though!).

[tgross35]

Makes sense, cc @jackpot51 for the redox portion.

[jackpot51]

This looks fine to me

[tgross35]

Thanks for the PR, and for the review!