Check if current GPU supports Vulkan DRM modifiers when `--backend=au…

…to` is used.

This works around ValveSoftware#1218 by making use of the new backend option added in ValveSoftware#1321,
but adds a check to automatically fall back to the SDL backend if the current
GPU does not support Vulkan DRM modifiers.

src/main.cpp

@@ -817,7 +817,14 @@ int main(int argc, char **argv)
 	if ( eCurrentBackend == gamescope::GamescopeBackend::Auto )
 	{
 		if ( g_pOriginalWaylandDisplay != NULL )
-			eCurrentBackend = gamescope::GamescopeBackend::Wayland;
+		    // Additional check if the current GPU supports Vulkan DRM modifiers
+            // Fallback to SDL if not supported (e.g Older AMD GPUs like Polaris 10/20)
+            if (vulkan_supports_modifiers()) {
+                eCurrentBackend = gamescope::GamescopeBackend::Wayland;
+            }
+            else {
+                eCurrentBackend = gamescope::GamescopeBackend::SDL;
+            }
 		else if ( g_pOriginalDisplay != NULL )
 			eCurrentBackend = gamescope::GamescopeBackend::SDL;
 		else