Use RPATH on Linux and Mac by default
Use RPATH on Linux and Mac by default

Makes it easier to run the tests by automatically adding the appropriate
rpath to executables.

Change-Id: Ia70a90a7c84f944b6963b87f10210baf494a35cf

wadejong/avogadrolibs,ghutchis/avogadrolibs,OpenChemistry/avogadrolibs,wadejong/avogadrolibs,cjh1/mongochemweb-avogadrolibs,OpenChemistry/avogadrolibs,OpenChemistry/avogadrolibs,ghutchis/avogadrolibs,ghutchis/avogadrolibs,cjh1/mongochemweb-avogadrolibs,ghutchis/avogadrolibs,OpenChemistry/avogadrolibs,wadejong/avogadrolibs,cjh1/mongochemweb-avogadrolibs,cjh1/mongochemweb-avogadrolibs,ghutchis/avogadrolibs,wadejong/avogadrolibs,OpenChemistry/avogadrolibs