Revert of Remove depenedency on GYP_DEFINES in clang gclient hook (patchset #2 id:20001 of https://codereview.chromium.org/2733043002/ )

Reason for revert:
update.py is used by non-chromium devs. See:
https://codereview.chromium.org/2749003002/

Original issue's description:
> Remove dependency on GYP_DEFINES in clang gclient hook
>
> The gold plugin is needed only for linux official builds. However, since
> it's only 17MB, it's better to always download it rather than having it
> depend on GYP_DEFINES.
>
> BUG=570091, 699210
>
> Review-Url: https://codereview.chromium.org/2733043002
> Cr-Commit-Position: refs/heads/master@{#455991}
> Committed: https://chromium.googlesource.com/chromium/src/+/57310cedbe5d558ba806b3f60f752b84e20a65eb

TBR=thakis@chromium.org,krasin@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=570091, 699210

Review-Url: https://codereview.chromium.org/2748973003
Cr-Original-Commit-Position: refs/heads/master@{#456729}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 081e3434463b81db9b72d96e4a4c5e8016f02b60
1 file changed