Don't build/run tests when cross compiling.
Don't build/run tests when cross compiling.

Summary:
Don't run the tests when cross compiling.  They executables
will be for the wrong architecture and will not work.

Reviewed By: djwatson

Differential Revision: D3772739

fbshipit-source-id: 289e2d3c4bab8fe87b591ab2ab5ba38d092e9cf6

facebook/wangle,facebook/wangle,facebook/wangle