apparently they suck at keeping their SDL distributions up to date

src/wx/main.cpp

@@ -29,6 +29,12 @@
 #include "EmuConfig.h"
 
 
+// blarg
+#ifndef SDL_PIXELFORMAT_RGBA32
+#define SDL_PIXELFORMAT_RGBA32 SDL_PIXELFORMAT_ABGR8888
+#endif // SDL_PIXELFORMAT_RGBA32
+
+
 wxIMPLEMENT_APP_NO_MAIN(wxApp_melonDS);