Add repro for gh11037 (ocaml#11047)

Signed-off-by: Stephen Sherratt <stephen@sherra.tt>

test/blackbox-tests/test-cases/pkg/ocamlformat/gh11037.t

@@ -0,0 +1,73 @@
+Exercise differences between the behavior of `dune fmt` when a lockdir is
+present and a lockdir is absent.
+
+  $ . ./helpers.sh
+  $ mkrepo
+  $ make_project_with_dev_tool_lockdir
+
+Make a fake ocamlformat package that appends a comment to the end of its input.
+  $ mkpkg ocamlformat <<EOF
+  > install: [
+  >   [ "sh" "-c" "echo '#!/bin/sh' > %{bin}%/ocamlformat" ]
+  >   [ "sh" "-c" "echo 'cat \$2' >> %{bin}%/ocamlformat" ]
+  >   [ "sh" "-c" "echo 'echo \$2 | grep .*.ml >/dev/null && echo \"(* formatted with fake ocamlformat *)\"' >> %{bin}%/ocamlformat" ]
+  >   [ "sh" "-c" "chmod a+x %{bin}%/ocamlformat" ]
+  > ]
+  > EOF
+
+The foo package depends on the bar package.
+  $ cat > dune-project <<EOF
+  > (lang dune 3.16)
+  > (package
+  >  (name foo)
+  >  (depends bar))
+  > EOF
+
+The foo executable depends on the bar library.
+  $ cat > dune <<EOF
+  > (executable
+  >  (public_name foo)
+  >  (libraries bar))
+  > EOF
+
+Without a .ocamlformat `dune fmt` does nothing.
+  $ touch .ocamlformat
+
+Run `dune fmt` before creating a lockdir, and print the file foo.ml before and
+after to demonstrate that it was formatted. Note that the package "bar" hasn't
+yet been defined, so the fact that `dune fmt` works indicates that dune did not
+attempt to build the package "foo".
+  $ cat foo.ml
+  let () = print_endline "Hello, world"
+  $ DUNE_CONFIG__LOCK_DEV_TOOL=enabled dune fmt
+  Solution for dev-tools.locks/ocamlformat:
+  - ocamlformat.0.0.1
+  File "foo.ml", line 1, characters 0-0:
+  Error: Files _build/default/foo.ml and _build/default/.formatted/foo.ml
+  differ.
+  Promoting _build/default/.formatted/foo.ml to foo.ml.
+  [1]
+  $ cat foo.ml
+  let () = print_endline "Hello, world"
+  (* formatted with fake ocamlformat *)
+
+Create a lockdir and define the package "bar". Note its install command is
+`false` so it will fail to install.
+  $ mkdir dune.lock
+  $ cat > dune.lock/lock.dune <<EOF
+  > (lang package 0.1)
+  > EOF
+  $ cat > dune.lock/bar.pkg <<EOF
+  > (version 0.0.1)
+  > (install (run false))
+  > EOF
+
+Now run `dune fmt` again. It attempts to build the project and its
+dependencies, and fails to install the dependency "bar".
+  $ DUNE_CONFIG__LOCK_DEV_TOOL=enabled dune fmt
+  File "dune.lock/bar.pkg", line 2, characters 14-19:
+  2 | (install (run false))
+                    ^^^^^
+  Error: Logs for package bar
+
+  [1]