Try again: in unix like system, set foreground process while running external command (#6273)

* Revert "Fix intermittent test crash (#6268)"

This reverts commit 555d9ee763.

* make a working version again

* try second impl

* add

* fmt

* check stdin is atty before acquire stdin

* add libc

* clean comment

* fix typo

src/main.rs

@@ -134,6 +134,14 @@ fn main() -> Result<()> {
 
     let parsed_nu_cli_args = parse_commandline_args(&nushell_commandline_args, &mut engine_state);
 
+    #[cfg(target_family = "unix")]
+    {
+        // This will block SIGTSTP, SIGTTOU, SIGTTIN, and SIGCHLD, which is required
+        // for this shell to manage its own process group / children / etc.
+        nu_system::signal::block();
+        nu_system::signal::set_terminal_leader()
+    }
+
     match parsed_nu_cli_args {
         Ok(binary_args) => {
             if let Some(t) = binary_args.threads {