The useful geant4-config tool will return the CLHEP include path but not the library path or the library itself with the '--libs' option, I think it should do. See also http://hypernews.slac.stanford.edu/HyperNews/geant4/get/installconfig/1476.html
In progress, will be resolved in 9.6
Fixed in tag cmake-V09-05-69, will be in 9.6 Release