Rollup merge of #88828 - FabianWolff:issue-88585, r=dtolnay

Use `libc::sigaction()` instead of `sys::signal()` to prevent a deadlock

Fixes #88585. POSIX [specifies](https://man7.org/linux/man-pages/man3/fork.3p.html) that after forking,
> to avoid errors, the child process may only execute async-signal-safe operations until such time as one of the exec functions is called.

Rust's standard library does not currently adhere to this, as evidenced by #88585. The child process calls [`sys::signal()`](https://github.com/rust-lang/rust/blob/7bf0736e130e2203c58654f7353dbf9575e49d5c/library/std/src/sys/unix/android.rs#L76), which on Android calls [`libc::dlsym()`](https://github.com/rust-lang/rust/blob/7bf0736e130e2203c58654f7353dbf9575e49d5c/library/std/src/sys/unix/weak.rs#L101), which is [**not**](https://man7.org/linux/man-pages/man7/signal-safety.7.html) async-signal-safe, and in fact causes a deadlock in the example in #88585.

I think the easiest solution here would be to just call `libc::sigaction()` instead, which [is](https://man7.org/linux/man-pages/man7/signal-safety.7.html) async-signal-safe, provides the functionality we need, and is apparently available on all Android versions because it is also used e.g. [here](https://github.com/rust-lang/rust/blob/7bf0736e130e2203c58654f7353dbf9575e49d5c/library/std/src/sys/unix/stack_overflow.rs#L112-L114).

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