Instrumented libraries: Remove dependence on GYP_DEFINES

This CL ports download_binaries.py and unpack_binaries.py from using
GYP_DEFINES to gn args.  Previously, there was a gotcha step where you
had to run 'gclient sync' with the right GYP_DEFINES to actually download
the prebuilt instrumented libraries.  This CL removes that step.

CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_chromium_msan_rel_ng;master.tryserver.chromium.linux:linux_chromium_chromeos_msan_rel_ng
R=eugenis@chromium.org
BUG=705072

Review-Url: https://codereview.chromium.org/2775913002
Cr-Original-Commit-Position: refs/heads/master@{#459630}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 5adb8c047852670be6c9d42114f3a17d44b6c56e
3 files changed
tree: c3011e7089df7fe94015fc2886ae1f76757b0aaa
  1. BUILD.gn
  2. OWNERS
  3. README.chromium
  4. binaries/
  5. blacklists/
  6. patches/
  7. scripts/