Fix checkCompatibility to work with clean build.
Fix checkCompatibility to work with clean build.

fengshao0907/servo,ccortezb/servo,Netflix/servo,ccortezb/servo,entelesis/servo,eonezhang/servo,sensaid/servo,brharrington/servo,sensaid/servo,eonezhang/servo,entelesis/servo,rspieldenner/servo,gorcz/servo,fengshao0907/servo,brharrington/servo