remove fetch-gn dependency on buildtools

This makes it possible to fetch GN without syncing DEPS.

To roll GN now, just update the three hashes in bin/fetch-gn.

buildtools is still a dependency of fetch-clang-format.

Bug: skia:7634

Change-Id: Ida6b516cfb0b306da73550875ab1ff97c9da6a64
Reviewed-on: https://skia-review.googlesource.com/107882
Reviewed-by: Hal Canary <halcanary@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
1 file changed