Fix building of raylib_opengl_interop on PLATFORM_DESKTOP_SDL (#3826)

I tested this with CMake. I don't know if the examples makefile
currently handles this case.

examples/others/raylib_opengl_interop.c

@@ -26,7 +26,7 @@
 
 #include "raylib.h"
 
-#if defined(PLATFORM_DESKTOP)
+#if defined(PLATFORM_DESKTOP) || defined(PLATFORM_DESKTOP_SDL)
     #if defined(GRAPHICS_API_OPENGL_ES2)
         #include "glad_gles2.h"       // Required for: OpenGL functionality 
         #define glGenVertexArrays glGenVertexArraysOES
@@ -163,4 +163,4 @@ int main(void)
     //--------------------------------------------------------------------------------------
 
     return 0;
-}
+}