To circumvent compilation errors with the older L4Android Linux kernel
version, the ballooning driver is included in the more recent L4Linux
kernel only. Moreover, to be able to maintain L4Android / L4Linux in a more
convenient way, e.g. to apply patches valid for both versions, we use
the same git clone that is used for L4Linux instead of using the upstream
L4Android version by applying patches.
Fixes#1390
Sebastian Sumpf
Stefan Kalkowski
Christian Helmuth
Norman Feske