Move cxa_demangle_stub.cc from base to libc++abi

On Android, cxa_demangle_stub.cc provides __cxa_demangle.  We use this to
prevent pulling in libc++abi's large demangler.

However, regular c++ code expects __cxa_demangle to be available simply by
linking against a c++ standard library.  Therefore, we move the stub into
libc++abi so other targets don't need to explicitly specify cxa_demangle_stub.cc
as a dependency.

This CL also includes a buildtools roll which includes 4 revisions:
https://chromium.googlesource.com/chromium/buildtools/+log/0b71401b977fba99eb0c7bb01bdb3338f45bd911..a9e946f166b73f9dc170129f6586a1e68efb0ab3

BUG=767901
R=thakis

Change-Id: I627833b1379ba938c07b3ab6645a775220a7aeb0
Reviewed-on: https://chromium-review.googlesource.com/1054198
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#558084}
3 files changed