This prevents multiple simultaneous runs of the analyzer from stomping
over each other (e.g. multiple runs of 'update-packages'). Certain
long-lived commands (like analyze, run, logs) are exempted once they've
done enough work to be safe from most stomping action.
This still doesn't make us entirely safe from craziness, e.g. if you're
half way through an 'update-packages' run and you call 'git pull', who
knows what state you'll end up in. But there's only so much one can do.
Fixes https://github.com/flutter/flutter/issues/2762
* working on making a faster flutter run restart
* clean up todos; fire events on isolate changes
* use the Flutter.FrameworkInitialization event
* review comments
Host tools can be found in the artifact cache directory for the host platform.
If a developer wants to use a local engine build instead, then provide an
--engine-build flag that selects the specific engine build variant.
This provides a fast way to iterate on changes to a Flutter app that only
involve updates to Dart code and do not require a full build and install
of the FLX and APK
