Have the dev_pkg make a different install root outside of the spheral-spack-tpls directory so that we can tar up the spheral-spack-tpls directory and use it with the build cache instead of having the install pkg script create it's own spack instance.
Also, have the --init-only command for tpl-manager load a spack environment as well to ensure it also creates a spack-package repo in the right spot.