...as discussed in 371cc81b "external/liborcus:
Fix Linux RPATH:"

* When an external module produces multiple libraries (that we all install) that
  depend on each other, they need to contain $ORIGIN in RPATH (strictly
  speaking, those that do not depend on any other libraries from the module
  would not need that, but it is harmless and easier to do that way).

* When an external module's libraries depend on other external modules'
  libraries, and (at least some of) those other external modules are not
  configuread as --with-system-*, they need to contain $ORIGIN in RPATH (again,
  for simplicity, some libraries may get that even if they would not strictly
  need it).

* Try to outsmart the external modules' libtool instances to not add (ultimately
  bogus) paths to RPATH for dependencies on libraries from external modules
  (either from the same module, or from anohter module not configured as
  --with-system-*).  The only time we do not outsmart libtool, and instead rely
  on it (hopefully?) doing the right thing is when a given external modules'
  libraries depend on libraries from excatly one other external module, and the
  latter is configured as --with-system-*.

* That outsmarting means that if an external library depends both on external
  libraries provided by modules not configured as --with-system-* (so RPATH
  contains $ORIGIN, and the outsmarting is not suppressed) and on external
  libraries provided by modules configured as --with-system-*:  Then if the
  latter are in unusual locations on the system that would require an RPATH
  entry (which might be provided via the corresponding "pkg-config --libs", say,
  and presumably would be honoured by libtool if we did not outsmart it), then
  those paths are now erroneously missing from RPATH.

* That outsmarting also causes linking of some utility applications in module
  redland to fail, but those are ultimately unused, so cut them off by patching
  their respective sub-directory Makefile.in.

Change-Id: Iec05b3568fbcf04987018322c328b769ae4f5dab