* systems/settings channel split

* merge textScaleFactor and alwaysUse24HourFormat into flutter/settings channel

* add debugOverrideAlwaysUse24HourFormat

* implement textScaleFactor on iOS

* address comments

* remove debugOverrideAlwaysUse24HourFormat

* clang-format

minikin::LineBreaker does not convert newline characters into line breaks
in its output.  Previously libtxt's version of LineBreaker container a patch
that added a large width offset for a newline in order to force wrapping to
the next line.  This works if the offset exceeds the paragraph's width
constraint.  But if the paragraph is laid out with infinite width, then the
text after the newline will continue on the current output line.

This change separates the paragraph's text into newline delimited blocks and
feeds each block separately to the minikin LineBreaker.

Also, libtxt was breaking the input styled text runs at newline boundaries.
This is no longer necessary.

The output_name property of a template is typically relative to the
root_build_dir rather than the target_gen_dir. This patch makes flutter_app
consistent with this pattern.

See: https://github.com/realm/jazzy/issues/791

This declaration makes it easier for Fuchsia to include Flutter in the system
image.

* Fix for issue 12526

Ensure that child isolates do not clear the dart_ui_state_ field present in the dart controller.

The commit https://github.com/flutter/engine/commit/dd1e0b59ece026737b05640cf020a6e590cfc10c implemented code to reset the dart_ui_state_ back to null when an isolate was being shutdown to ensure there was no use after free issues when the main isolate exeutes Isolate.current.kill() it however it was also clearning the field when a child isolate was shutdown causing SEGVs later.

* Address code format issues.

Just log them as errors

* Add dependency on chromium/src/build for Mac/iOS build

Preparation for migrating to mac_toolchain.py for installing/configuring
Xcode versions on the Mac build bots.

* Exclude third_party/chromium_build from licence script

It's used only at build time to fetch and install the correct Xcode
version.

maxIntrinsicWidth is the sum of the width of all lines in the input
(if the width were any smaller, the renderer might have to wrap a line)

minIntrinsicWidth is the maximum width of a word (if the paragraph were
any narrower, the renderer would have to truncate a word)

It was accidently removed in a5e26f1f.

This is for Fuchsia where we would like it to be located at //third_party/flutter.

This registers a test font manager that maps all fonts to the Ahem font

Fixes https://github.com/flutter/flutter/issues/12513

They help the analysis service identify packages and are now mandatory on Fuchsia.

ClearDartWrapper will delete this SceneBuilder, causing deletion of the
LayerBuilder

This was used by AndroidSurfaceSoftware but is now obsolete

Make sure we await for the file writing to complete before reporting that compilation is done. (#4210)