tools and docs: clean up gyp-specific things

BUG=skia:

DOCS_PREVIEW= https://skia.org/?cl=5770

Change-Id: Iadc436a68cbf7ec0d1dd3c019072eb28bf589bb6
Reviewed-on: https://skia-review.googlesource.com/5770
Commit-Queue: Hal Canary <halcanary@google.com>
Reviewed-by: Mike Klein <mtklein@chromium.org>
6 files changed