To reduce compile-times and avoid some overhead to binary size, this will modify some of our
generic functions to use non-generic inner functions where possible. The inner functions are
marked carefully with `#[inline(never)]` to prevent being inlined by LLVM at their callsites
While looking for generic functions to optimize, I have also taken the opportunity to annotate
public non-generic getters and setters with `#[inline]` to ensure that LLVM will inline them
across crate boundaries. By default, only generic functions are automatically inlined, and
only when enabling fat LTO are constant functions reliably inlined across crate boundaries.
Although this is used in apps that use `tokio`, if we're going to
support `smol`, this seems suboptimal to require.
This assumes the function will be called by a tokio executor if the
`tokio` feature is used. Otherwise it can be spawned from any executor.
That should be consistent with everything else.
This fails to compile without either the `tokio` or `smol` feature. This
seems reasonable, since `zbus` also fails to compile in that case.
`rustix` and `libc` are already in the dependency tree, and `rustix`
follows IO safety rules, so use those.
We can use a pipe to get the PID of the double-forked process.
