Allow PROCESSOR_IDENTIFIER into build env.
Allow PROCESSOR_IDENTIFIER into build env.

PROCESSOR_IDENTIFIER is necessary for the python platform module to correctly
identify the bitness of the host machine.

See http://hg.python.org/cpython/file/4190568ceda0/Lib/platform.py#l1175

R=iannucci@chromium.org

Review URL: https://chromiumcodereview.appspot.com/24447002

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@225073 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build