main: add "cores" and "threads" schedulers to help text

This was missing before.

Author: aykevl

main.go

@@ -1542,7 +1542,7 @@ func main() {
 	opt := flag.String("opt", "z", "optimization level: 0, 1, 2, s, z")
 	gc := flag.String("gc", "", "garbage collector to use (none, leaking, conservative, custom, precise, boehm)")
 	panicStrategy := flag.String("panic", "print", "panic strategy (print, trap)")
-	scheduler := flag.String("scheduler", "", "which scheduler to use (none, tasks, asyncify)")
+	scheduler := flag.String("scheduler", "", "which scheduler to use (none, tasks, cores, threads, asyncify)")
 	serial := flag.String("serial", "", "which serial output to use (none, uart, usb, rtt)")
 	work := flag.Bool("work", false, "print the name of the temporary build directory and do not delete this directory on exit")
 	interpTimeout := flag.Duration("interp-timeout", 180*time.Second, "interp optimization pass timeout")