Revert of Roll buildtools ecc8e253..4cbd4550 (patchset #1 id:1 of https://codereview...

Revert of Roll buildtools ecc8e253..4cbd4550 (patchset #1 id:1 of https://codereview.chromium.org/1234033003/)

Reason for revert:
Reverting this, it broke the mac build complaining about duplicate objects for obj/chrome/browser/ui/browser_ui/external_protocol_dialog.o .

http://build.chromium.org/p/chromium.mac/builders/Mac%20GN/builds/12724/steps/generate_build_files/logs/stdio

Original issue's description:
> Roll buildtools ecc8e253..4cbd4550
>
>   4cbd455 Roll GN 43e357b..ec34450 (r333203..r338735)
>
>     8a80090 Replace base::str[n]casecmp with helper functions.
>     3f87569 Make .s files generate cflags for ninja
>     d82b231 Add ninja dependency reference to gen written files.
>     b4729ae Update the GN style guide on target naming.
>     20982dc Add a //nogncheck anntation to GN include checker
>     9bcde38 Update gn bootstrap.py to handle latest chromium changes
>     b030801 Remove old/unused atomicops code
>     ddcc0a4 Convert gn_unittests to run exclusively on Swarming
>     8440203 Normalize paths in GN.
>     874d7ad GN: Throw an error for duplicate object files.
>     3dab5fe Windows precompiled header support in GN.
>     e6dae46 Add more string_util functions to base namespace.
>     b341306 Move more string_util functions to base namespace.
>     634ad43 tools/gn: Update docs to refer to 'public_configs'.
>     17b32ad Move EndsWith to base namespace.
>     44ce0ec Move StartsWith[ASCII] to base namespace.
>     6ee6fd6 Move safe_strerror to posix directory and the base namespace.
>     5316b8c Update //tools/gn/docs/reference.md
>     0bfa8a8 clang/win: Make everything work in a GN build.
>
> TBR=brettw@chromium.org
>
> Committed: https://crrev.com/1f73ee1a87b386ac231cbee807d55cfccda0bfd6
> Cr-Commit-Position: refs/heads/master@{#338772}

TBR=brettw@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/1234713003

Cr-Commit-Position: refs/heads/master@{#338782}