Adds the BIONIC toolchain to the SDK when building with --bionic. 

Only affects SDK build, not Chrome.

NOTRY=true
BUG=344575
TEST=build_sdk.py --bionic

see also parent issue:
  https://code.google.com/p/chromium/issues/detail?id=344574

Review URL: https://codereview.chromium.org/170973003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251870 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251870