sk_tools/Resources: optional SK_TOOLS_REQUIRE_RESOURCES flag

BUG=skia:7842
Change-Id: I1ce7d12308cd8ee101163d73dfc79f2d2155c632
Reviewed-on: https://skia-review.googlesource.com/123425
Auto-Submit: Hal Canary <halcanary@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
Reviewed-by: Florin Malita <fmalita@chromium.org>
3 files changed