System extensions
Gardenhouse produces immutable systems, this means that software may
not be traditionally installed through emerge or any other
package manager.
However, since it can still be useful to extend the base system with
more software, say a development extension, or a gaming extension,
Gardenhouse uses sysext to
allow merging prebuilt images onto the system /usr.
This feature may be disabled by setting the global USE flag
-sysext.