fix: exit from Main with exit code rather than voiding

src/main/wacc/Main.scala

@@ -82,9 +82,9 @@ def compile(filename: String, outFile: Option[File] = None)(using
 def main(args: Array[String]): Unit =
   OParser.parse(cliParser, args, CliConfig()) match {
     case Some(config) =>
-      compile(
+      System.exit(compile(
         config.file.getAbsolutePath,
         outFile = Some(File(".", config.file.getName.stripSuffix(".wacc") + ".s"))
-      )
+      ))
     case None =>
   }