Add .exp for remote testing

[vries]

The nvptx-none-run.exp facilitates a setup where compiling a test and running the test is done on the same machine.

It would be good to have a .exp file that facilitates a setup where compiling a test is done on one machine, and running the test on another. Put differently, nvptx-none-run.exp is based on sim.exp. We want a similar file based on, say unix.exp.

As a start, we could split nvptx-none-run.exp into two parts, one that is specific to compiling tests, and another that is specific to using sim.exp.