Instrumented libraries: add a target for pre-built libraries.

With use_prebuilt_instrumented_libraries=1 in GYP_DEFINES, binaries are now
unpacked from archive and placed into output dir.

BUG=462636
R=glider@chromium.org
TBR=thakis@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/1017053003

Cr-Commit-Position: refs/heads/master@{#321804}
3 files changed