[nostalgia/core/gba] Fix event cycle and add to setter for event handler

src/nostalgia/core/sdl/core.cpp

@@ -9,9 +9,12 @@
 #include <SDL.h>
 
 #include <nostalgia/core/gfx.hpp>
+#include <nostalgia/core/core.hpp>
 
 namespace nostalgia::core {
 
+static event_handler g_eventHandler = nullptr;
+
 void draw(Context *ctx);
 
 ox::Error init(Context *ctx) {
@@ -41,6 +44,10 @@ ox::Error run(Context *ctx) {
 	return OxError(0);
 }
 
+void setEventHandler(event_handler h) {
+	g_eventHandler = h;
+}
+
 uint64_t ticksMs() {
 	return SDL_GetTicks();;
 }