https://bugs.freedesktop.org/show_bug.cgi?id=80419
--- Comment #157 from andrew.m.mcmahon@gmail.com --- So I've had a go at compiling mesa with the fix applied. I'll list what I've done here to be absolutely clear.
Cloned a new copy of mesa
Downloaded the patch file from the link Michel posted into the same directory Patched the source file
patch src/gallium/auxiliary/cso_cache/cso_cache.c mesa.patch
Compiled the driver with a handy script:
I override (but don't replace) Debian's drivers with the compiled mesa drivers:
Rebooted and cleared out my mesa shader cache from ~/.cache and ~/.steam/steam/steamapps/shadercache/
The stability of the game is noticeably improved - I was able to play right through the first tutorial battle, fight several more battles up to the point where you build Alien Containment. Must've played it for at least an hour.
I've not tested whether Enemy Within any other game is affected by the change however.