Roll src/buildtools/ aec56e260..0dd5c6f98 (3 commits)

https://chromium.googlesource.com/chromium/buildtools.git/+log/aec56e26079f..0dd5c6f980d2

$ git log aec56e260..0dd5c6f98 --date=short --no-merges --format='%ad %ae %s'
2018-06-29 scottmg Revert "Remove libcpp_is_static"
2018-06-29 scottmg Re-add .gitignore for GN
2018-06-28 thomasanderson Remove libcpp_is_static

Created with:
  roll-dep src/buildtools

TBR: dpranke@chromium.org
Bug: 858852, v8:7900
Change-Id: Ie887a2a54932703505369516ca42bf44c19242db
Reviewed-on: https://chromium-review.googlesource.com/1121046Reviewed-by: Scott Graham <scottmg@chromium.org>
Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Scott Graham <scottmg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#571628}

DEPS

@@ -121,7 +121,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling build tools
   # and whatever else without interference from each other.
-  'buildtools_revision': 'aec56e26079fba121e589006a88b7cbc1c398cfb',
+  'buildtools_revision': '0dd5c6f980d22be96b728155249df2da355989d9',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling SwiftShader
   # and whatever else without interference from each other.