Because INSIDE_DUNE is set for sandboxing Dune does not perform root discovery
in tests. That is why for each call to Dune we specify manually the `root`
directory in these tests.

  $ ln -s realroot linkroot

  $ cd linkroot

  $ dune build

Absolute path with symlinks won't match with Dune's root path in which symlinks
are resolved:
  $ dune ocaml merlin dump-config --format=json "$PWD/realsrc" --root="."
  Path $TESTCASE_ROOT/linkroot/realsrc is not in dune workspace ($TESTCASE_ROOT/realroot).

Absolute path with resolved symlinks will match with Dune's root path:
  $ dune ocaml merlin \
  > dump-config --format=json "$(pwd | sed 's/linkroot/realroot/')/realsrc" \
  > --root="." | jq '
  > include "dune";
  > .[0] | merlinPathSummary'
  {
    "module_name": "Foo",
    "source_path": "_build/default/realsrc/foo"
  }


Dune ocaml-merlin also accepts paths relative to the current directory
  $ dune ocaml merlin dump-config --format=json "realsrc" --root="." | jq '
  > include "dune";
  > .[0] | merlinPathSummary'
  {
    "module_name": "Foo",
    "source_path": "_build/default/realsrc/foo"
  }

  $ cd realsrc

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

  $ dune ocaml merlin dump-config --format=json "." --root=".." | jq '
  > include "dune";
  > .[0] | merlinConfigSummary(["INDEX", "STDLIB", "SOURCE_ROOT", "B", "S", "FLG", "UNIT_NAME"])'
  {
    "module_name": "Foo",
    "source_path": "_build/default/realsrc/foo",
    "config": [
      [
        "INDEX",
        "$TESTCASE_ROOT/realroot/_build/default/realsrc/.foo.eobjs/cctx.ocaml-index"
      ],
      [
        "STDLIB",
        "/OCAMLC_WHERE"
      ],
      [
        "SOURCE_ROOT",
        "$TESTCASE_ROOT/realroot"
      ],
      [
        "B",
        "$TESTCASE_ROOT/realroot/_build/default/realsrc/.foo.eobjs/byte"
      ],
      [
        "S",
        "$TESTCASE_ROOT/realroot/realsrc"
      ],
      [
        "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"
        ]
      ],
      [
        "UNIT_NAME",
        "dune__exe__Foo"
      ]
    ]
  }
