Requesting help with libtool RPATH stuff

[coypu%sdf.org@localhost]

Hi folks,

I'd like to make a lua package install to PREFIX/subdirectory.
It makes a library liblove.so.0 and an executable love which links
against it.
It apparently doesn't add its own PREFIX/subdirectory/lib to RPATH.

What's the correct way to add this RPATH?

I've added this package as wip/love010, if someone prefers to see for
themselves.