
https://github.com/flutter/flutter/issues/22338#issuecomment-425794734 shows almost 1 minute being spent on the `Resolving Dependencies` step alone. Possibly this needs to go higher still, but this should be a good start.
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