This was causing trouble with Fuchsia, since mksnapshot was built and run on
Linux which supports trap handlers, while Fuchsia does not yet. This change
causes the external references to match between Fuchsia and Linux.

Bug: chromium:772057
Change-Id: I8e8f3539e3f5c4b798c364101ef2d16b5137f16d
Reviewed-on: https://chromium-review.googlesource.com/706109Reviewed-by: Mircea Trofin <mtrofin@chromium.org>
Commit-Queue: Eric Holk <eholk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48408}