set exit code EXIT_FAILURE when --build-solutions fails

main/main.cpp

@@ -2434,9 +2434,11 @@ bool Main::iteration() {
 		auto_build_solutions = false;
 		// Only relevant when running the editor.
 		if (!editor) {
+			OS::get_singleton()->set_exit_code(EXIT_FAILURE);
 			ERR_FAIL_V_MSG(true, "Command line option --build-solutions was passed, but no project is being edited. Aborting.");
 		}
 		if (!EditorNode::get_singleton()->call_build()) {
+			OS::get_singleton()->set_exit_code(EXIT_FAILURE);
 			ERR_FAIL_V_MSG(true, "Command line option --build-solutions was passed, but the build callback failed. Aborting.");
 		}
 	}