* Revert "Reverting package changes until I can figure out how to fix Windows. (#14007)"
This reverts commit 6fda8ee821.
* Make prepare_package run on Windows
* Revert "Fixed output validation. (#14005)"
This reverts commit d84398db72.
* Revert "Update package prep script to do async process execution and emit output as it happens. (#13918)"
This reverts commit b7169c1d95.
- Switches to async process execution, which now shows output as it happens instead of in chunks when the process completes
- Now uses ProcessManager so that it may be mocked for the test.
- Adds in the download and install of mingit on Windows.
- Updated package dependencies because of added dependency on process package.
This simply updates the package dependencies by running flutter update-packages --force-upgrade.
I'm doing this with no other changes, because the last time I tried that, redness occurred. I want to isolate the problem to a "clean" update of the packages.
It looks like the plugins device_info, connectivity, and url_launcher haven't yet had their gradle configurations updated, so they fail when trying to build with the new gradle. I did not upgrade for those three packages only (in flutter_gallery) until we are ready to fix them (fixing them for master will break them for alpha users, so we need to do an alpha roll to do that).
