GN: Add write_runtime_deps variable

Allows targets to use runtime_deps at build-time.

BUG=593416

Review URL: https://codereview.chromium.org/1804303004

Cr-Original-Commit-Position: refs/heads/master@{#384411}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 0f8ad42ac1a6b159655c51bf7095ff2d21ae540f
12 files changed
tree: ab443833fa3659c54017f37a068e809c70031281
  1. tools/