[nostalgia/core/gba] Add IRQ system

src/nostalgia/core/gba/irq.arm.cpp

@@ -0,0 +1,20 @@
+/*
+ * Copyright 2016 - 2020 gtalent2@gmail.com
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+// NOTE: this file is compiled as ARM and not THUMB, so don't but too much in
+// here
+
+#include "irq.hpp"
+
+namespace nostalgia::core {
+
+void isr() {
+	REG_IF = IntId_vblank;
+}
+
+}