mkvendor: fix echoed build commands

cm.mk.template uses PRODUCT_NAME := cm___DEVICE__

Change-Id: I063fc4b93d90ebb034637bf3e92d83c77aa439ca
Merge branch 'cm-10.1' into martincz
build: merge CyanogenMod

Change-Id: I2ae8f9e466c65e3de7976f5cdd2dbb6e6ce76060