[perl #60608] [PATCH] Fix install when libdir is different from "$prefix/lib"

[Mark Glines via RT]

Thanks, applied in r33663.

Note that our Roadmap [1] places an overhaul of the installation tools
("pdd30-install"), slated to occur before our January 20th release.  As
such, the code affected by this patch will likely be subject to change
(and hopefully, improvement) at that point.

[1] https://trac.parrot.org/parrot/wiki/ParrotRoadmap