home: Allow for builds without a home partition

This should allow platforms that currently do not have support for an extra home
partition to still be buildable. Longer term, we should consider how to solve
this problem for those systems, as users will not have space to use for
persistence between operating system flashes.

Change-Id: I78d6c1d9d7b707c57e0bbf5db3d31629f88760f1
1 file changed