compiler: restore ability to pass -prod option to run and runrepl. (#3095)

vlib/compiler/compiler_options.v

@@ -0,0 +1,23 @@
+// Copyright (c) 2019 Alexander Medvednikov. All rights reserved.
+// Use of this source code is governed by an MIT license
+// that can be found in the LICENSE file.
+
+module compiler
+
+pub fn get_v_options_and_main_command(args []string) ([]string,string) {
+	mut options := []string
+	mut potential_commands := []string
+	for i := 0; i < args.len; i++ {
+		a := args[i]
+		if !a.starts_with('-') {
+			potential_commands << a
+			continue
+		}else{
+			options << a
+			if a in ['-o', '-os', '-cc', '-cflags'] { i++ }
+		}
+	}
+	// potential_commands[0] is always the executable itself, so ignore it
+	command := if potential_commands.len > 1 { potential_commands[1] } else { '' }
+	return options, command
+}