Add sonic board
Add sonic board

Basic definitions, these builds probably won't work for a while.

BUG=chromium:219692
TEST=unittests

Change-Id: Ief7846c968e923b201e0e265be66496300eaf41a
Reviewed-on: https://gerrit.chromium.org/gerrit/47396
Reviewed-by: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>
Commit-Queue: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>
Tested-by: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>

chadversary/chromiumos.chromite,chadversary/chromiumos.chromite,bpsinc-native/src_third_party_chromite,bpsinc-native/src_third_party_chromite,bpsinc-native/src_third_party_chromite