Simplify _readScreen2 for non-mobile builds

Removes an unnecessary allocation while keeping the codepath that was supposedly necessary on android.

src/Graphics/OpenGLContext/mupen64plus/mupen64plus_DisplayWindow.cpp

@@ -252,23 +252,21 @@ void DisplayWindowMupen64plus::_readScreen2(void * _dest, int * _width, int * _h
 	if (_dest == nullptr)
 		return;
 
-	u8 *pBufferData = (u8*)malloc((*_width)*(*_height) * 4);
-	if (pBufferData == nullptr)
-		return;
-	u8 *pDest = (u8*)_dest;
-
 #if !defined(OS_ANDROID) && !defined(OS_IOS)
 	GLint oldMode;
 	glGetIntegerv(GL_READ_BUFFER, &oldMode);
 	if (_front != 0)
 		glReadBuffer(GL_FRONT);
 	else
 		glReadBuffer(GL_BACK);
-	glReadPixels(0, m_heightOffset, m_screenWidth, m_screenHeight, GL_RGBA, GL_UNSIGNED_BYTE, pBufferData);
+	glReadPixels(0, m_heightOffset, m_screenWidth, m_screenHeight, GL_RGB, GL_UNSIGNED_BYTE, _dest);
 	glReadBuffer(oldMode);
 #else
+	u8 *pBufferData = (u8*)malloc((*_width)*(*_height) * 4);
+	if (pBufferData == nullptr)
+		return;
+	u8 *pDest = (u8*)_dest;
 	glReadPixels(0, m_heightOffset, m_screenWidth, m_screenHeight, GL_RGBA, GL_UNSIGNED_BYTE, pBufferData);
-#endif
 
 	//Convert RGBA to RGB
 	for (s32 y = 0; y < *_height; ++y) {
@@ -283,6 +281,7 @@ void DisplayWindowMupen64plus::_readScreen2(void * _dest, int * _width, int * _h
 	}
 
 	free(pBufferData);
+#endif
 }
 
 graphics::ObjectHandle DisplayWindowMupen64plus::_getDefaultFramebuffer()