test(melange): demonstrate error in melange compilation trying to build

@ALL (ocaml#6485)

Signed-off-by: Antonio Nuno Monteiro <[email protected]>

test/blackbox-tests/test-cases/melange/public.t/run.t

@@ -32,3 +32,73 @@ Build js files
 Path to app_B is non-relative (broken)
   $ node _build/default/$output/my_project/c.js
   buy it
+
+  $ dune clean
+  $ dune build @all
+  File "my_project/app/dune", line 1, characters 0-78:
+  1 | (library
+  2 |  (name app)
+  3 |  (public_name pkg.app)
+  4 |  (libraries lib)
+  5 |  (modes melange))
+  Error: No rule found for my_project/app/.app.objs/byte/app.cmi
+  File "my_project/app/dune", line 1, characters 0-78:
+  1 | (library
+  2 |  (name app)
+  3 |  (public_name pkg.app)
+  4 |  (libraries lib)
+  5 |  (modes melange))
+  Error: No rule found for my_project/app/.app.objs/byte/app.cmt
+  File "my_project/app/dune", line 1, characters 0-78:
+  1 | (library
+  2 |  (name app)
+  3 |  (public_name pkg.app)
+  4 |  (libraries lib)
+  5 |  (modes melange))
+  Error: No rule found for my_project/app/.app.objs/byte/app__B.cmi
+  File "my_project/app/dune", line 1, characters 0-78:
+  1 | (library
+  2 |  (name app)
+  3 |  (public_name pkg.app)
+  4 |  (libraries lib)
+  5 |  (modes melange))
+  Error: No rule found for my_project/app/.app.objs/byte/app__B.cmt
+  File "my_project/app/dune", line 1, characters 0-78:
+  1 | (library
+  2 |  (name app)
+  3 |  (public_name pkg.app)
+  4 |  (libraries lib)
+  5 |  (modes melange))
+  Error: No rule found for my_project/app/.app.objs/byte/app__B.cmti
+  File "my_project/lib/dune", line 1, characters 0-61:
+  1 | (library
+  2 |  (name lib)
+  3 |  (public_name pkg.lib)
+  4 |  (modes melange))
+  Error: No rule found for my_project/lib/.lib.objs/byte/lib.cmi
+  File "my_project/lib/dune", line 1, characters 0-61:
+  1 | (library
+  2 |  (name lib)
+  3 |  (public_name pkg.lib)
+  4 |  (modes melange))
+  Error: No rule found for my_project/lib/.lib.objs/byte/lib.cmt
+  File "my_project/lib/dune", line 1, characters 0-61:
+  1 | (library
+  2 |  (name lib)
+  3 |  (public_name pkg.lib)
+  4 |  (modes melange))
+  Error: No rule found for my_project/lib/.lib.objs/byte/lib__A.cmi
+  File "my_project/lib/dune", line 1, characters 0-61:
+  1 | (library
+  2 |  (name lib)
+  3 |  (public_name pkg.lib)
+  4 |  (modes melange))
+  Error: No rule found for my_project/lib/.lib.objs/byte/lib__A.cmt
+  File "my_project/lib/dune", line 1, characters 0-61:
+  1 | (library
+  2 |  (name lib)
+  3 |  (public_name pkg.lib)
+  4 |  (modes melange))
+  Error: No rule found for my_project/lib/.lib.objs/byte/lib__A.cmti
+  [1]
+