toolchain_build: Update binutils to 2.25
toolchain_build: Update binutils to 2.25

The binutils 2.25 release is out, and it supports arm-nacl
targets with no local patches.  The previous 2.24-based version
had no local patches, but was using an unreleased snapshot of the
2.24 branch.  Now we are back on an official release version.

Unlike the 2.24 branch, the 2.25 branch of upstream git still
contains the subdirectories that are only included in gdb
releases and not in binutils releases.  To build from the git
repository and get the same effect as building from the release
tarball, some new machinations are required to stub out the
builds of the subdirectories not relevant to binutils.

BUG= none
TEST= toolchain trybots
R=bradnelson@google.com

Review URL: https://codereview.chromium.org/831343002

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@14245 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client