Update dependency bazelbuild/buildtools to latest version
Update dependency bazelbuild/buildtools to latest version

Included changes:

  - c802c3b06ba674e8a76d04c0677d153ab9f660c9 Address golint warnings
  - 25dab36ca7324be602b34f18bc76a447e3d157d9 unused_deps: support cquery (#1030)
  - 9263785502fa2d4f8e31c26b90d7baef3a0bcb0e Implement --output_json (#1060)
  - 6f5bf4e2b30489597ac6a89055083a507f5de471 Support \u and \U Unicode escapes (#1054) (#1055)
  - 7e1946809955d50c38622efc2037244b226bae02 Fix symbols considered unused when referenced as types (#...

BAZEL_BUILDTOOLS_VERSION_REV_ID: c802c3b06ba674e8a76d04c0677d153ab9f660c9
Change-Id: I304418fb629912ea045abb36b6cdd2ae8015d3ab

google/copybara,google/copybara,google/copybara