spack-psi/env/merlin/sysconfigs/config.yaml

config:
  install_tree:
    root: /afs/psi.ch/sys/spack-rhel7
    projections:
      all: '{name}/{version}/{compiler.name}/{compiler.version}'
      ^mpi: '{name}/{version}/{^mpi.name}/{^mpi.version}/{compiler.name}/{compiler.version}'