Bump libc to 0.2.171 to use sigaction for AIX

[xingxue-ibm]

Change to use sa_sigaction instead of sa_union.__su_sigaction, now that the libc crate 0.2.171 implementation for AIX defines sa_sigaction as a direct member of struct sigaction, aligning it with implementations on other similar platforms. (rust-lang/libc#4250).

[daltenty]

Gentle ping, you can't build jobserver right now on AIX:

error[E0609]: no field `sa_union` on type `sigaction`
   --> /home/buildusr/.cargo/registry/src/index.crates.io-d11c229612889eed/jobserver-0.1.32/src/unix.rs:399:17
    |
399 |             new.sa_union.__su_sigaction = sigusr1_handler;
    |                 ^^^^^^^^ unknown field
    |
    = note: available fields are: `sa_sigaction`, `sa_mask`, `sa_flags`

[daltenty]

LGTM from the AIX perspective

[weihanglo]

Thanks! Looks reasonable.

[weihanglo]

We might also want to bump libc to 0.2.171 in Cargo.toml, so people will not accidentally get older versions and fail to compile.

[xingxue-ibm]

Good point! Changed as suggested, thanks!

[weihanglo]

Thanks. Ping me again if I forget to publish a new version today or tomorrow

[weihanglo]

jobserver@0.1.33 is out.

[xingxue-ibm]

Thank you, @weihanglo!