My name is Edwin Smith and I work for Feral Interactive. We don't support the
mesa drivers due to the stability issues compared to the closed source drivers
however we can pass on any crash logs and if it helps some complimentary XCOM
keys to the members of the driver team to help with the debugging effort.

The crash looks like a complete GPU hang that locks up the entire card. If it
helps I can look into getting exact instructions on how to attach apitrace to
the Steam release.