Revert of [gn] Switch gcc bots to gn (patchset #3 id:40001 of https://codereview.chromium.org/2124263002/ )

Reason for revert:
There are a bunch of goma errors on the gcc bot now. Maybe connected to this CL.

https://build.chromium.org/p/tryserver.v8/builders/v8_linux_gcc_compile_rel/builds/19068

Original issue's description:
> [gn] Switch gcc bots to gn
>
> BUG=chromium:474921
>
> Committed: https://crrev.com/73f154ba601dc70c4007968fa902d4beacba4393
> Cr-Commit-Position: refs/heads/master@{#37580}

TBR=vogelheim@chromium.org,jochen@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:474921

Review-Url: https://codereview.chromium.org/2130303002
Cr-Commit-Position: refs/heads/master@{#37603}