test: print flags for vendored projects (ocaml#9521)

Signed-off-by: Rudi Grinberg <[email protected]>

test/blackbox-tests/test-cases/github7034.t/run.t

@@ -96,6 +96,16 @@ But when lang dune is 3.3 or higher the warning becomes an error:
     -short-paths
     -keep-locs))
   Leaving directory 'outer'
+  $ dune printenv outer/vendored/inner --root=outer --field flags
+  Entering directory 'outer'
+  (flags
+   (-w
+    @[email protected]@30..39@[email protected]@[email protected]@67@69-40
+    -strict-sequence
+    -strict-formats
+    -short-paths
+    -keep-locs))
+  Leaving directory 'outer'
   $ dune build --root=outer
   Entering directory 'outer'
   File "vendored/inner/inner.ml", line 6, characters 11-18:
@@ -104,6 +114,15 @@ But when lang dune is 3.3 or higher the warning becomes an error:
   Error (warning 69 [unused-field]): unused record field x.
   Leaving directory 'outer'
   [1]
+  $ pat="\-o [./a-zA-Z_]\{1,\}.cmx"
+  $ log=outer/_build/log
+  $ grep -o "$pat" $log | sort
+  -o .outer.eobjs/native/dune__exe__Outer.cmx
+  -o vendored/inner/.inner.objs/native/inner.cmx
+  $ grep "$pat" $log | sort | grep -n -E -o "\-w [^ ]+"
+  1:-w @[email protected]@30..39@[email protected]@[email protected]@67@69-40
+  2:-w @[email protected]@30..39@[email protected]@[email protected]@67@69-40
+  2:-w -a
 
 This is unexpected as vendored projects should be built according to their
 declared dune-project rather than the dune-project of the outer project.