* Roll Fuchsia buildtools to 85907c59e97527d79bbfdfd849d8e85c24959cc5
This also updates Flutter buildroot to a6e52dbb776c45cc8c57d7143b8eb8b2e762fdfb
which disables -Wtautological-constant-compare temporarily until
https://reviews.llvm.org/D39462 lands in clang. This is in line with
Fuchsia's compiler options.
* Apply clang-format diffs
No logical changes. This applies clang-format from the latest Fuchsia
buildtools to the engine codebase.
