Updates for rootless v2

[L1ghtmann]

Prereqs:

• https://github.com/DragonBuild/lib/pull/3
• https://github.com/DragonBuild/include/pull/3

Useful but not strictly necessary:

• https://github.com/DragonBuild/frameworks/pull/3
• https://github.com/DragonBuild/src/pull/2
  • Note that this is necessary if 01e86763fc0f6d9ed349ef66ed442934a5331580 is merged

Changes:

• Removes explicit substrate link for tweaks as Logos handles this now (see above)
• Update supplied rpaths to support variable jbroot

Resolves #138

NOTE not ready yet -- have to figure out dynamic libroot link