Fixes https://github.com/flutter/flutter/issues/11952

* Roll Skia and enable API guards
* Update licenses

The Windows build does not have an appropriate target_cpu because it is incomplete and does not build the engine.

Roll Dart to be95b916ddf0af2b204286a438e7169e3bb2c67a.

This somehow introduces text relocations even though we always use -fPIC.

Roll Dart VM to daa38a2ea21d290e45adb509dc60418b22ec7eba for fix to Thumb profile sample collection.

Roll buildroot to b0b836db790abff26695a944224a4934480f2f48.

* Build Flutter patched-sdk with kernel artifacts

* Switch to new dart_host_toolchain argument mechanism to let dart patch_sdk know of host_toolchain.

* Update dart dependency

* Updated licenses

* Rename dart dependencies tag so they have just 'dart_'-prefixed dart's names.

* Fix indentation and line breaks for newly added deps.

* Add toolchain for windows host

* Update dart revision

* Licenses

* Update licenses

* Revert changes to licenses_third_party

Use the value specified in build/config/ios/ios_sdk.gni in the buildroot
repo.

Updates buildroot to 4d1c1fd7103d6daba559e456a6a68e4385bb28f1

Earlier, when the —enable-vulkan flag was specified, the out directory name was determined by the other flags specified to `flutter/tools/gn`. But, the build itself was Vulkan enabled. Now that we are going to add the vulkan target to buildbot, we want to clearly delineate a Vulkan enabled build from a non-Vulkan enabled one.

Update targets only included in host_debug_unopt.

This reverts commit f5d0004e.

Previously, —unoptimized builds on Android would include debug symbols but still would be optimized. This killed the experience in the debugger on Android.

* Remove references to unused GN files and flags.
* Fix Linux build.

https://github.com/flutter/flutter/issues/4866