Roll buildtools 26b7e66950..f6d165d9d8

  In order to roll GN cf557ff0..87530f97 (r502818:r503394) and pick up
  the following changes:

  338348fc Add bundle_contents_dir property to create_bundle.
  f669a8d3 Fix GN bootstrap

TBR=dpranke@chromium.org

Change-Id: I5cb32543446461eaadb880b69c276d80aaca4a8f
Reviewed-on: https://chromium-review.googlesource.com/677194Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#503413}

DEPS

@@ -57,7 +57,7 @@ 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': '26b7e66950e910d7cdd4c3faf780cca25a5ce39a',
+  'buildtools_revision': 'f6d165d9d842ddd29056c127a5f3a3c5d8e0d2e3',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling SwiftShader
   # and whatever else without interference from each other.