Introduce a new test for the alarm(2) system call.
This test verifies the behavior of setting, cancelling,
and re-arming alarms, ensuring correct signal delivery
and return values.
The implementation for confstr is straightforward. Most of the constants
return 1 on both musl and glibc. The only constant that doesn't is
required for Fish.
I also switched an #[unsafe(no_mangle)] from my last patch back
to a #[no_mangle] because we need to bump cbindgen. #[unsafe(no_mangle)]
is required for Rust 2024.
Zero