Revert of Use GN in simple chrome builders (patchset #1 id:1 of https://codereview.chromium.org/1918713005/ )
Revert of Use GN in simple chrome builders (patchset #1 id:1 of https://codereview.chromium.org/1918713005/ )

Reason for revert:
Well, I fixed a bunch of things, but it got late and I'm still hitting bugs, so I'm going to try to flip this back to GYP and see if that works, at least (through MB).

https://build.chromium.org/p/chromium.chromiumos/builders/ChromiumOS%20amd64-generic%20Compile/builds/17407

The last error makes it look like we might be missing a few targets that chromiumos_preflight needs, but I might've also just gotten the build labels wrong in the GN build.

I suggest we try again tomorrow and flip the trybots at the same time so we can be consistent and see the trybots working first.

Original issue's description:
> Use GN in simple chrome builders
>
> BUG=605154
>
> Committed: https://crrev.com/78685fb274d05ee48e5425dc2ce4f5ba7b2dce81
> Cr-Commit-Position: refs/heads/master@{#389914}

TBR=stevenjb@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=605154

Review URL: https://codereview.chromium.org/1921003009

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#389998}

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