If you want to use this package as your default system ruby, as root
create symbolic links like so (overwriting any previous default):
 ln -sf ${PREFIX}/bin/ruby25 ${PREFIX}/bin/ruby
 ln -sf ${PREFIX}/bin/erb25 ${PREFIX}/bin/erb
 ln -sf ${PREFIX}/bin/irb25 ${PREFIX}/bin/irb
 ln -sf ${PREFIX}/bin/rdoc25 ${PREFIX}/bin/rdoc
 ln -sf ${PREFIX}/bin/ri25 ${PREFIX}/bin/ri
 ln -sf ${PREFIX}/bin/rake25 ${PREFIX}/bin/rake
 ln -sf ${PREFIX}/bin/gem25 ${PREFIX}/bin/gem
