Avoid allocating in pre_exec closure (#2213)

Author: ammgws

src/subprocess.rs

@@ -11,7 +11,7 @@ pub fn spawn_process(cmd: &str, args: &[&str]) -> io::Result<()> {
     // Safety: libc::daemon() is async-signal-safe
     unsafe {
         proc.pre_exec(|| match libc::daemon(0, 0) {
-            -1 => Err(io::Error::other("Failed to detach new process")),
+            -1 => Err(io::Error::last_os_error()),
             _ => Ok(()),
         });
     }