Issues with Vulkan Renderer

[efrainm23]

I wanted to bring attention an issue with artifacts on the screen that look like black boxes when using the Vulkan renderer in the Flycast core referenced in the following issue thread for Retroarch:

https://github.com/libretro/RetroArch/issues/16973

It apparently started happening since Retroarch version 1.19. I can see this core has not been updated in a while, and maybe something can be done on the core side to resolve the issue instead of waiting for Retroarch to be updated to fix whatever broke it. Switching to glcore driver works to avoid the issue. One over person also was able to use shaders to fix the issue, but that did not work for me.