Refactor OS exit code to be `EXIT_SUCCESS` by default

- `Main::setup` early exits (failure or `--help`/`--version`) now
  consistently return `EXIT_FAILURE` or `EXIT_SUCCESS` on all platforms,
  instead of 255 on some and a Godot Error code on others.
- `Main::start` now returns the exit code, simplifying the handling of early
  failures.
- `Main::iteration` needs to explicit set the exit code in OS if it errors
  out.
- Web and iOS now properly return `OS::get_exit_code()` instead of 0.

1 files changed, 6 insertions, 5 deletions

diff --git a/platform/ios/godot_ios.mm b/platform/ios/godot_ios.mm
index 5e66c8b47b..9d35d43344 100644
--- a/platform/ios/godot_ios.mm
+++ b/platform/ios/godot_ios.mm
@@ -102,15 +102,16 @@ int ios_main(int argc, char **argv) {
 
 	Error err = Main::setup(fargv[0], argc - 1, &fargv[1], false);
 
-	if (err == ERR_HELP) { // Returned by --help and --version, so success.
-		return 0;
-	} else if (err != OK) {
-		return 255;
+	if (err != OK) {
+		if (err == ERR_HELP) { // Returned by --help and --version, so success.
+			return EXIT_SUCCESS;
+		}
+		return EXIT_FAILURE;
 	}
 
 	os->initialize_modules();
 
-	return 0;
+	return os->get_exit_code();
 }
 
 void ios_finish() {