cli: allow flag to be set multi time (#8256)

examples/cli.v

@@ -28,10 +28,17 @@ fn main() {
 	greet_cmd.add_flag(Flag{
 		flag: .int
 		name: 'times'
-		value: '3'
+		value: ['3']
 		description: 'Number of times the message gets printed.'
 	})
+	greet_cmd.add_flag(Flag{
+	 	flag: .string
+	 	name: 'fun'
+	 	multipe: true
+	 	description: 'Just a dumby flags to show multiple.'
+	})
 	cmd.add_command(greet_cmd)
+	cmd.setup()
 	cmd.parse(os.args)
 }
 
@@ -61,6 +68,12 @@ fn greet_func(cmd Command) {
 			}
 		}
 	}
+	fun := cmd.flags.get_strings('fun') or {
+		panic('Failed to get `fun` flag: $err')
+	}
+	for f in fun {
+		println('fun: ${f}')
+	}
 }
 
 fn greet_pre_func(cmd Command) {