Add wrappers for posix_spawn related functions (#2475)

* Add wrappers for posix_spawn related functions

Closes #1740

* Use Errno::result helper

* chore: add changelog entry for PR

* Add tests for posix_spawn function

---------

Co-authored-by: kosayoda <[email protected]>
Co-authored-by: Cameron Nemo <[email protected]>

Author: 3 people

changelog/2475.added.md

@@ -0,0 +1 @@
+Added wrappers for `posix_spawn` API

src/lib.rs

@@ -184,6 +184,18 @@ pub mod unistd;
 #[cfg(any(feature = "poll", feature = "event"))]
 mod poll_timeout;
 
+#[cfg(any(
+    target_os = "freebsd",
+    target_os = "haiku",
+    target_os = "linux",
+    target_os = "netbsd",
+    apple_targets
+))]
+feature! {
+    #![feature = "process"]
+    pub mod spawn;
+}
+
 use std::ffi::{CStr, CString, OsStr};
 use std::mem::MaybeUninit;
 use std::os::unix::ffi::OsStrExt;