Since we do not support gcc < 5 any more, we can switch to C++14 now.
Gcmole is the only tool preventing this currently.

R=mstarzinger@chromium.org

Bug: v8:9687, v8:9690
Change-Id: Ie7fee25061bdf6f1e7f156bc150b7142c824f5d1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1787426Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63595}