Fix crash when both FlutterFragmentActivity and FlutterFragment are destroyed and recreated (#25851)

* Revert "Roll Dart SDK from 3cc6cdab8eaf to b8f4018535fa (2 revisions) (#25885)"

This reverts commit d84caa73.

* Revert "Roll Dart SDK from 6ecae204598d to 3cc6cdab8eaf (2 revisions) (#25877)"

This reverts commit 03bd2e35.

* Revert "Roll Dart SDK from b98a1eec5eb5 to 6ecae204598d (1 revision) (#25874)"

This reverts commit 7ce62261.

* Revert "Roll Dart SDK from 8c109a734bdc to b98a1eec5eb5 (1 revision) (#25873)"

This reverts commit e623c095.

* Revert "Roll Dart SDK from ee8eb0a65efa to 8c109a734bdc (1 revision) (#25872)"

This reverts commit 01b9db82.

* Revert "Roll Dart SDK from 6397e8b91103 to ee8eb0a65efa (1 revision) (#25869)"

This reverts commit 4aae6b32.

* Revert "Roll Dart SDK from 1e3e5efcd47e to 6397e8b91103 (18 revisions) (#25861)"

This reverts commit 74ac0103.

https://skia.googlesource.com/skia.git/+log/3010f3d79193..5276ba274b38

2021-04-30 bsalomon@google.com Add --reducedshaders to fm

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/skia-flutter-autoroll
Please CC jcgregorio@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/master/autoroll/README.md

* Revert "Roll Dart SDK from b5ff349bffc8 to a45eaf6402c3 (1 revision) (#25837)"

This reverts commit 5180937c.

* Revert "Roll Dart SDK from 90993fcb8554 to b5ff349bffc8 (1 revision) (#25834)"

This reverts commit 02446a1b.

* Revert "Roll Dart SDK from 21aa7f8cbde8 to 90993fcb8554 (1 revision) (#25832)"

This reverts commit 497e816f.

* Revert "Roll Dart SDK from 8bab67dad50b to 21aa7f8cbde8 (1 revision) (#25829)"

This reverts commit 48f0068d.

* Revert "Roll Dart SDK from 1e3e5efcd47e to 8bab67dad50b (8 revisions) (#25822)"

This reverts commit 45708201.

https://github.com/flutter/flutter/issues/69221

This allows creating build folders for macOS cross compilation

https://github.com/flutter/flutter/issues/69221