Add missing import to toolchain_build.py
Add missing import to toolchain_build.py

It was broken by r12628

R=mcgrathr@chromium.org
BUG=none

Review URL: https://codereview.chromium.org/141583007

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@12633 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

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