mkvendor: fix echoed build commands

cm.mk.template uses PRODUCT_NAME := cm___DEVICE__

Change-Id: I063fc4b93d90ebb034637bf3e92d83c77aa439ca
Merge branch 'cm-10.1' of github.com:CyanogenMod/android_build into cm-10.1

Conflicts:
	tools/device/mkvendor.sh