Code review comment for lp://staging/~pundiramit/linaro-android-build-tools/labt

Ok, I've discussed this with Vishal: the goal of this is to enable produced linaro_android_build_cmds.sh to work without the SOURCE_OVERLAY when not really needed. Since we do not use this script for actually building Android on jenkins, it's ok if this script has an override for SOURCE_OVERLAY (eg. perhaps set it to SOURCE_OVERLAY=ignore; if you want to do it any other way, that's fine as well).

However, the actual jenkins build should not allow that to be set in the build config (on android-build.linaro.org).