I've just rebuilt Mesa again with your patch, no CCache or anything this time,
just in case. I'm still getting no clouds on the loading screen (you can see
the stars as white dot and the names, but there's no colour, everything is just
black and white) and then when it gets "in game" the menu is there, but the
screen is still just white.

I wonder if the card is specific here:
OpenGL renderer string: Radeon RX 580 Series (POLARIS10, DRM 3.26.0,
4.18.3-1-clear, LLVM 8.0.0)
OpenGL core profile version string: 4.5 (Core Profile) Mesa 18.3.0-devel
(git-9e5e3a8ead)