Ability to specify initial Instruments launch timeout from subliminal-test

[jazzychad]

We are noticing that it always takes X runs of the subliminal runner to successfully wait for Instruments to launch in CI - so basically the first X-1 builds are wasted time while we wait for the Instruments timeout to become high enough.

It would be handy to be able to specify the initial (or some additional) Instruments launch timeout value (in seconds probably) from the subliminal-test arguments from command line.

[wearhere]

Sounds fine to me. I'm surprised you see that it consistently takes instruments a certain amount of time to launch--it varies widely between runs both here on Travis and locally using Jenkins--but ¯_(ツ)_/¯. I'd probably implement this using an environment variable rather than another argument to subliminal-test--it has so many already and this is kinda advanced usage.