Relax glibc requirement to 2.17

This CL adds a hack that removes the symbol __cxa_thread_atexit_impl
from libc.so in the sysroots.  In addition, it also rolls the sysroots
and updates the expected deps to reflect the symbol no longer being
required.

BUG=749077
R=thestig@chromium.org

Change-Id: I7501d45b8ecff66e97287002bea9ee1e351348c5
Reviewed-on: https://chromium-review.googlesource.com/592279
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#490541}
9 files changed