Roll buildtools ecc8e253..4cbd4550

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

Review URL: https://codereview.chromium.org/1234033003

Cr-Commit-Position: refs/heads/master@{#338772}