PROTON-464: Install Ruby bindings to install prefix if specified. If the user provides a CMAKE_INSTALL_PREFIX on the command line, then that directory is used to install the Ruby language bindings. If no install prefix is specified then the Ruby bindings honor the directory specified by the Ruby VM itself.
qpid/proton/trunk/proton-c/bindings/CMakeLists.txt
qpid/proton/trunk/proton-c/bindings/ruby/CMakeLists.txt