Added armv7l to list of known architectures.
Added armv7l to list of known architectures.

Mapping of architectures to platforms was missing armv7l.

BUG=
TEST= trybots
R=binji@chromium.org

Review URL: https://codereview.chromium.org/138813002

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@12612 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

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