Add implementation of start and stop commands for iOS.

Don’t give a scary error about not being able to run on Android if there’s no Android device connected.

Forward additionalArgs in run_mojo.dart

Just log, don’t exit when the user is missing access to a command. Prevents inappropriately-failing tests.

Just log, don’t exit when the user is missing access to a command. Prevents inappropriately-failing tests.

Beginning implementation of IOSDevice. Implements list and install.

In 0.0.15, additional cmdline arguments were not dropped, but now in 0.0.16, the arguments are no longer forwarded.
This patchset would restore this forwarding functionality.

For example, the following command is intended to pass `enable-multiprocess` to the mojo_shell.
`enable-multiprocess` in 0.0.16 does not get passed along, but this patchset would allow it to once again.

pub run sky_tools -v --very-verbose run_mojo \
	--mojo-path $MOJO_DIR/src \
	--app app.flx --android \
	-- \
	--enable-multiprocess

Also update tests to be compatible with the presence of iOS and add tests for list and install.

Add listen command and basic test, and don’t do unnecessary repeated work when listening or poking the android server.

Add optional prefix to runCommandAndStreamOutput for logs commands.

Also add unchecked runSync wrapper and use it in places where command failures don’t matter.

Add stop command and supporting Android support.

Fix sky_tools build command to look for package-root in global args

Also refactors the command line assembling to make a bit more sense.

Fixes #53

This makes the 'package-root' option universal for sky_tools and configures the
ArtifactStore with it statically at startup. The actual sky_engine revision
is computed on demand.

run_mojo: Add --mojo-release and --mojo-debug flags.

The flags control which build of mojo to run (Debug or Release).
Default is Release.

Make cached artifact location mirror local builds more closely