test: reproduce dune exec -w crash with pkg management

Signed-off-by: Antonio Nuno Monteiro <anmonteiro@gmail.com>

test/blackbox-tests/test-cases/pkg/gh10959.t

@@ -0,0 +1,87 @@
+Repro `dune exec --watch` crash with pkg management
+
+  $ . ./helpers.sh
+
+  $ mkrepo
+  $ add_mock_repo_if_needed
+
+
+  $ mkdir _multiple
+  $ cat >_multiple/dune-project <<EOF
+  > (lang dune 3.13)
+  > (package (name foo) (allow_empty))
+  > (package (name bar) (allow_empty))
+  > EOF
+
+  $ cat >dune-project <<EOF
+  > (lang dune 3.13)
+  > (pin
+  >  (url file://$PWD/_multiple)
+  >  (package (name foo))
+  >  (package (name bar)))
+  > (package
+  >  (name main)
+  >  (depends foo bar))
+  > EOF
+
+  $ cat >dune <<EOF
+  > (executable
+  >  (name x))
+  > EOF
+  $ cat >x.ml <<EOF
+  > let () = print_endline "x"
+  > EOF
+
+  $ dune pkg lock
+  Solution for dune.lock:
+  - bar.dev
+  - foo.dev
+
+  $ dune exec -w ./x.exe
+  File "src/dune_engine/build_system.ml", line 67, characters 11-17:
+  File "src/dune_engine/build_system.ml", line 67, characters 11-17: Assertion
+  failed
+  Raised at Dune_engine__Build_system.State.update_build_progress_exn in file
+    "src/dune_engine/build_system.ml", line 67, characters 11-23
+  Called from Dune_engine__Build_system.State.start_rule_exn in file
+    "src/dune_engine/build_system.ml" (inlined), lines 76-77, characters 4-79
+  Called from Dune_engine__Build_system.Exported.execute_rule_impl in file
+    "src/dune_engine/build_system.ml", line 462, characters 41-66
+  Called from Fiber__Scheduler.exec in file "vendor/fiber/src/scheduler.ml",
+    line 76, characters 8-11
+  Re-raised at Stdune__Exn.raise_with_backtrace in file
+    "otherlibs/stdune/src/exn.ml", line 38, characters 27-56
+  Called from Fiber__Scheduler.exec in file "vendor/fiber/src/scheduler.ml",
+    line 76, characters 8-11
+  Re-raised at Stdune__Exn.raise_with_backtrace in file
+    "otherlibs/stdune/src/exn.ml", line 38, characters 27-56
+  Called from Fiber__Scheduler.exec in file "vendor/fiber/src/scheduler.ml",
+    line 76, characters 8-11
+  Re-raised at Stdune__Exn.raise_with_backtrace in file
+    "otherlibs/stdune/src/exn.ml", line 38, characters 27-56
+  Called from Fiber__Scheduler.exec in file "vendor/fiber/src/scheduler.ml",
+    line 76, characters 8-11
+  Re-raised at Stdune__Exn.raise_with_backtrace in file
+    "otherlibs/stdune/src/exn.ml", line 38, characters 27-56
+  Called from Fiber__Scheduler.exec in file "vendor/fiber/src/scheduler.ml",
+    line 76, characters 8-11
+  Re-raised at Stdune__Exn.raise_with_backtrace in file
+    "otherlibs/stdune/src/exn.ml", line 38, characters 27-56
+  Called from Fiber__Scheduler.exec in file "vendor/fiber/src/scheduler.ml",
+    line 76, characters 8-11
+  Re-raised at Stdune__Exn.raise_with_backtrace in file
+    "otherlibs/stdune/src/exn.ml", line 38, characters 27-56
+  Called from Fiber__Scheduler.exec in file "vendor/fiber/src/scheduler.ml",
+    line 76, characters 8-11
+  Re-raised at Stdune__Exn.raise_with_backtrace in file
+    "otherlibs/stdune/src/exn.ml", line 38, characters 27-56
+  Called from Fiber__Scheduler.exec in file "vendor/fiber/src/scheduler.ml",
+    line 76, characters 8-11
+
+  I must not crash.  Uncertainty is the mind-killer. Exceptions are the
+  little-death that brings total obliteration.  I will fully express my cases. 
+  Execution will pass over me and through me.  And when it has gone past, I
+  will unwind the stack along its path.  Where the cases are handled there will
+  be nothing.  Only I will remain.
+  [1]
+