Suggestion: Flag to rez-build for running tests

[brent...@gmail.com]

It's really cool how newer versions of rez have a "run_on" option for tests that allows you to automatically run test suites with rez-build (pre_install).  One request we've got from users is the ability to toggle the test suite running in rez-build itself.  Like, they would like to run "rez-build --run-tests [optional test names]" .  The developers don't always want to run the tests on every rez-build so they don't define the pre_install run_on configuration in the package.py.  We can run rez-build and then rez-test.  But from an automation point of view, you have to make sure that the --path parameter in rez-build and the --paths parameter in rez-test match up.  Combining that functionality into rez-build would be helpful.

Possible?

-Brent