Summary:
The xlog test currently fails due to the way that CMake invokes the compiler
with absolute path names.  In the future we should probably update the xlog
code with the ability to strip off some directory prefixes.

Reviewed By: yfeldblum

Differential Revision: D6817547

fbshipit-source-id: 40f08d56d0199c21808a4046ebc1a3a9d70a33e9