Instead of using "$ORIGIN/../lib" just use "$ORIGIN".
Also be explicit in configuring the relative RPATH. We don't want
to assume a default relative path, in case more targets are addded,
out of caution.
Change-Id: I3b7f5e8de7be8bb30aca3b433212113d876c4163
Reviewed-on: https://code.wireshark.org/review/31647
Reviewed-by: Peter Wu <peter@lekensteyn.nl>