Roll buildtools 5941c1b3df..9c9fd97928

  In order to roll GN a3bcd204..7f29218b (r567268:r570036) and pick up
  the following changes:

  5321951e Change "gn check" to report all incorrect include
  6955d08c [gn] Doc: Fix toochain typo and clarify the toolchain syntax.

TBR=dpranke@chromium.org

Change-Id: I74be13541e722d5ad5fd8199e6242928ffb084d2
Reviewed-on: https://chromium-review.googlesource.com/1113747Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#570059}

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': '5941c1b3df96c1db756a2834343533335c394c4a',
+  'buildtools_revision': '9c9fd97928dd45a0d9738af90f7c03b082f1216f',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling SwiftShader
   # and whatever else without interference from each other.