[CMake] Determining what test number in parallel runs.

[Utkarsh Ayachit]

Is there any mechanism (e.g. special environment variables that ctest
sets, etc.) that I can use to identify the track or number of the test
being run when running tests in parallel (with ctest -j )?

I want to sent up multiple x-servers and launch parallel tests that
popup windows on separate x-servers. But to set the DISPLAY variable
correctly for the test, I need to know what "track" the test is being
run on. Any means to do that?

Thanks,
Utkarsh