Missing shared library search path

[m-diers]

When creating hpx with lci 1.7.7 from a non-standard installation directory, there is a link error with the lci libraries. The interdependent lci libraries are not found.
This can be fixed temporarily during the build of lci using the following example:

cmake -DCMAKE_INSTALL_PREFIX=/opt/lci/ \
      -DCMAKE_INSTALL_RPATH='$ORIGIN/../lib' \
      ../lci-src/

This should already be fixed internally.