  $ dune build @check

  $ ocamlc_where="$(ocamlc -where)"
  $ export BUILD_PATH_PREFIX_MAP="/OCAMLC_WHERE=$ocamlc_where:$BUILD_PATH_PREFIX_MAP"

We dump the config for Foo and Bar modules but the pp.exe preprocessor
should appear only once since only Foo is using it.

  $ dune ocaml merlin dump-config $PWD
  Bar
  ((STDLIB /OCAMLC_WHERE)
   (EXCLUDE_QUERY_DIR)
   (B
    $TESTCASE_ROOT/_build/default/.foo.objs/byte)
   (S
    $TESTCASE_ROOT)
   (FLG
    (-w
     @1..3@5..28@30..39@43@46..47@49..57@61..62-40
     -strict-sequence
     -strict-formats
     -short-paths
     -keep-locs
     -g)))
  Foo
  ((STDLIB /OCAMLC_WHERE)
   (EXCLUDE_QUERY_DIR)
   (B
    $TESTCASE_ROOT/_build/default/.foo.objs/byte)
   (S
    $TESTCASE_ROOT)
   (FLG
    (-pp
     $TESTCASE_ROOT/_build/default/pp/pp.exe))
   (FLG
    (-w
     @1..3@5..28@30..39@43@46..47@49..57@61..62-40
     -strict-sequence
     -strict-formats
     -short-paths
     -keep-locs
     -g)))
