Revert of Add helpful error messages to check_gn_headers.py (patchset #3 id:40001 of https://codereview.chromium.org/2891363004/ )

Reason for revert:
This CL is likely causing massive failures:

https://build.chromium.org/p/chromium.linux/builders/Linux%20Builder/builds/84473
to
https://build.chromium.org/p/chromium.linux/builders/Linux%20Builder/builds/84498

and

https://build.chromium.org/p/chromium.linux/builders/Linux%20Builder%20%28dbg%29/builds/111528
to
https://build.chromium.org/p/chromium.linux/builders/Linux%20Builder%20%28dbg%29/builds/111542

Original issue's description:
> Add helpful error messages to check_gn_headers.py
>
> Before running check_gn_headers.py, it is necessary to build all
> in order to get the dependency info from the compiler. Directly
> checking whether rebuilding is needed by running a build dry run
> takes too long, so some heuristics are used instead.
>
> BUG=661774
>
> Review-Url: https://codereview.chromium.org/2891363004
> Cr-Commit-Position: refs/heads/master@{#474588}
> Committed: https://chromium.googlesource.com/chromium/src/+/0ceaba5ef538ce1780578d5e948641bc27f5829b

TBR=dpranke@chromium.org,tfarina@chromium.org,wychen@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=661774

Review-Url: https://codereview.chromium.org/2905863002
Cr-Original-Commit-Position: refs/heads/master@{#474649}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: d3c2681426db53550547f2bc115c3f72ba40f276
2 files changed