Roll buildtools to b92ff9

This roll includes 2 revisions [1] and should be a no-op on all bots.

[1] https://chromium.googlesource.com/chromium/buildtools/+log/9a65473..b92ff91

R=thakis@chromium.org

Review-Url: https://codereview.chromium.org/2948863002
Cr-Commit-Position: refs/heads/master@{#480978}

DEPS

@@ -56,7 +56,7 @@ 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': '9a65473a7e8f39f04fd134e69470ab1b48514b0e',
+  'buildtools_revision': 'b92ff913082ac9223b48eee9a5fc9db91346279a',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling SwiftShader
   # and whatever else without interference from each other.