tools/nolibc: add _exit()

_exit() is the faster variant of exit(), skipping all cleanup actions.
As nolibc does not perform any cleanup anyways, the implementation is
trivial.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Acked-by: Willy Tarreau <w@1wt.eu>

tools/include/nolibc/sys.h

@@ -300,11 +300,17 @@ void sys_exit(int status)
 }
 
 static __attribute__((noreturn,unused))
-void exit(int status)
+void _exit(int status)
 {
 	sys_exit(status);
 }
 
+static __attribute__((noreturn,unused))
+void exit(int status)
+{
+	_exit(status);
+}
+
 
 /*
  * pid_t fork(void);