Add test for the same mld's in different scopes

This case on the other hand is allowed

test/blackbox-tests/test-cases/odoc-unique-mlds/diff-scope/scope1/jbuild

@@ -0,0 +1,5 @@
+(jbuild_version 1)
+
+(library
+ ((name scope1)
+  (public_name scope1)))

test/blackbox-tests/test-cases/odoc-unique-mlds/diff-scope/scope2/jbuild

@@ -0,0 +1,5 @@
+(jbuild_version 1)
+
+(library
+ ((name scope2)
+  (public_name scope2)))

test/blackbox-tests/test-cases/odoc-unique-mlds/run.t

@@ -1,4 +1,5 @@
-  $ $JBUILDER build @doc -j1 --display short --root .
+Duplicate mld's in the same scope
+  $ $JBUILDER build @doc -j1 --display short --root ./same-scope 2>&1 | grep -v Entering
           odoc _doc/odoc.css
           odoc _doc/root.lib1/page-index.odoc
           odoc _doc/root.lib1/page-test.odoc
@@ -14,3 +15,21 @@
           odoc _doc/root.lib2/index.html
           odoc _doc/root.lib2/test.html
           odoc _doc/root.lib2/Root_lib2/.jbuilder-keep,_doc/root.lib2/Root_lib2/index.html
+
+Duplicate mld's in different scope
+  $ $JBUILDER build @doc -j1 --display short --root ./diff-scope 2>&1 | grep -v Entering
+          odoc _doc/odoc.css
+          odoc _doc/scope1/page-foo.odoc
+          odoc _doc/scope1/page-index.odoc
+        ocamlc scope1/.scope1.objs/scope1.{cmi,cmo,cmt}
+          odoc _doc/scope2/page-foo.odoc
+          odoc _doc/scope2/page-index.odoc
+        ocamlc scope2/.scope2.objs/scope2.{cmi,cmo,cmt}
+          odoc _doc/scope1/scope1.odoc
+          odoc _doc/scope2/scope2.odoc
+          odoc _doc/scope1/foo.html
+          odoc _doc/scope1/index.html
+          odoc _doc/scope1/Scope1/.jbuilder-keep,_doc/scope1/Scope1/index.html
+          odoc _doc/scope2/foo.html
+          odoc _doc/scope2/index.html
+          odoc _doc/scope2/Scope2/.jbuilder-keep,_doc/scope2/Scope2/index.html