Workspaces also allow you to set the env for a context:

  $ dune printenv --profile default
  (flags
   (-w -40 -machin))
  (ocamlc_flags
   (-g -verbose))
  (ocamlopt_flags (-g))
  (melange.compile_flags (-g))
  (c_flags ())
  (cxx_flags ())
  (link_flags ())
  (menhir_flags ())
  (coq_flags (-q))
  (js_of_ocaml_flags ())
  (js_of_ocaml_build_runtime_flags ())
  (js_of_ocaml_link_flags ())
