Add preprocessor-only test for submodule imports

llvm-svn: 145490
diff --git a/clang/test/Modules/submodules.cpp b/clang/test/Modules/submodules.cpp
index 6d541f6..fd1426d 100644
--- a/clang/test/Modules/submodules.cpp
+++ b/clang/test/Modules/submodules.cpp
@@ -1,4 +1,5 @@
 // RUN: rm -rf %t
+// RUN: %clang_cc1 -Eonly -fmodule-cache-path %t -fauto-module-import -I %S/Inputs/submodules %s -verify
 // RUN: %clang_cc1 -fmodule-cache-path %t -fauto-module-import -I %S/Inputs/submodules %s -verify
 
 __import_module__ std.vector;