cmake: Simplify passing of RPATH options
cmake: Simplify passing of RPATH options

Since all project are statically built, these options only make sense
in the context of the inner project.

NIRALUser/SPHARM-PDM,NIRALUser/SPHARM-PDM,bpaniagua/SPHARM-PDM,NIRALUser/SPHARM-PDM,bpaniagua/SPHARM-PDM,bpaniagua/SPHARM-PDM