This reverts commit e22f99743b.
Adding the exit(exitCode) fixes the hang.
Tested by running `fx run-host-tests` with a topaz checkout.
Verified the hang before, no hang after.
Flutter Tools
Tools for building Flutter applications.
To run the tests, ensure that no devices are connected,
then navigate to flutter_tools and execute:
../../bin/cache/dart-sdk/bin/pub run test -j1