Previously install-sysroot.py relied on gyp. This should be fixed now.
This way, tools/node/fetch_deps.py can also be used to fetch
dependencies when building V8 to run V8 tests from a Node.js checkout.

R=machenbach@chromium.org

Change-Id: Ic4ee425d6ae744c32f604d14fbfdb0554a00c486
Reviewed-on: https://chromium-review.googlesource.com/962421
Commit-Queue: Yang Guo <yangguo@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51939}