* `weak`: both directory schemes are allowed, packages only built on classical hosts
* `middle`: both directory schemes are allowed, packages can be built anywhere
* `hard`: both directory schemes are allowed, packages only built on "merged `/usr`" hosts
* `weak`: both directory schemes are allowed, packages only built on classical hosts
* `middle`: both directory schemes are allowed, packages can be built anywhere
* `hard`: both directory schemes are allowed, packages only built on "merged `/usr`" hosts