Allow CLI arguments when using dune build

Desired Behavior

Currently, dune exec allows the use of -- to provide the rest of the arguments to the executable. This is a nice feature since I don't have to write

dune build
./path/to/main.exe <args>

Is there a reason why this behaviour doesn't exist for dune build?
The first example that comes to my mind is dune runtest. This is an alias for dune build @runtest

Example

Let's take an alcostest file:

(* Build with `ocamlbuild -pkg alcotest simple.byte` *)

(* A module with functions to test *)
module To_test = struct
  let lowercase = String.lowercase_ascii
end

(* The tests *)
let test_lowercase1 () =
  Alcotest.(check string) "same string" "hello!" (To_test.lowercase "hELLO!")

let test_lowercase2 () =
  Alcotest.(check string) "same string" "hello!" (To_test.lowercase "hello!")

(* Run it *)
let () =
  let open Alcotest in
  run "Utils"
    [
      ("case1", [ test_case "Lower case" `Quick test_lowercase1 ]);
      ("case2", [ test_case "Lower case" `Quick test_lowercase2 ]);
    ]

Running dune runtest will result in:

❯ dune runtest
Testing `Utils'.
This run has ID `RO6YPVEX'.

  [OK]          case1          0   Lower case.
  [OK]          case2          0   Lower case.

Full test results in `~/dune_test/_build/default/tests/_build/_tests/Utils'.
Test Successful in 0.000s. 2 tests run.

Now if I just want to execute case1 I have to write

dune exec -- tests/main.exe test "case1"

Resulting in:

❯ dune exec -- tests/main.exe test "case1"
Testing `Utils'.
This run has ID `E674JOW4'.

  [OK]          case1          0   Lower case.
  [SKIP]        case2          0   Lower case.

Full test results in `~/dune_test/_build/_tests/Utils'.
Test Successful in 0.000s. 1 test run.

I'd like to be able to write:

dune runtest -- "case1"

Is there a reason why this is not possible right now?

Start by comparing how the dune exec command parses arguments after -- with how dune build and the runtest alias handle command-line arguments. Confirm the intended behavior using the issue's dune runtest -- "case1" example; done means the command forwards those arguments to the test executable while preserving existing build and alias behavior.