On 'canImport' of Clang submodules of modules with an umbrella header, attempt to infer the submodule

Resolves rdar://124163264

Author: artemcm

lib/ClangImporter/ClangImporter.cpp

@@ -2187,7 +2187,7 @@ ModuleDecl *ClangImporter::Implementation::loadModuleClang(
   // Verify that the submodule exists.
   clang::Module *submodule = clangModule;
   for (auto &component : path.getSubmodulePath()) {
-    submodule = submodule->findSubmodule(component.Item.str());
+    submodule = submodule->findOrInferSubmodule(component.Item.str());
 
     // Special case: a submodule named "Foo.Private" can be moved to a top-level
     // module named "Foo_Private". Clang has special support for this.