One multiple library package

[philderbeast]

We have one project with many packages. Could we put these all in the one multiple library package?

-- cabal.project
packages:
    simple-smt
    ghc-tcplugins-trace/ghc-tcplugins-trace
    thoralf-theory
    thoralf-encode
    thoralf-plugin
    thoralf-plugin-rows
    thoralf-plugin-uom
    thoralf-plugin-defs
    uom-quantity
    uom-plugin
    uom-plugin-defs
    uom-plugin-tutorial
    uom-plugin-examples
    uom-th
    build
tests: True
write-ghc-environment-files: always