Sync Dawn's DEPS via gclient and point CMake at them

Instead of having GN try to sync the repos (which was causing
a race condition when tint and dawn were built simultaneously),
we'll just sync them the usual way and point CMake at them
using configure defines.

This also takes a more careful look at the CMake settings we
were using for Dawn to disable stuff we don't need to build
(e.g. their tests and benchmarks).

Needed https://dawn-review.googlesource.com/c/dawn/+/270815 to land
so we could configure all the necessary deps.

Change-Id: Idd98895fe696953aae931e0dc2621d3f1cc9256d
Bug: b/455807680
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/1091757
Auto-Submit: Kaylee Lubick <kjlubick@google.com>
Reviewed-by: Eric Boren <borenet@google.com>
Commit-Queue: Kaylee Lubick <kjlubick@google.com>
Commit-Queue: Eric Boren <borenet@google.com>
6 files changed