Add missing test header

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@145710 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Modules/Inputs/diamond.h b/test/Modules/Inputs/diamond.h
new file mode 100644
index 0000000..0ae3c4f
--- /dev/null
+++ b/test/Modules/Inputs/diamond.h
@@ -0,0 +1 @@
+__import_module__ diamond_bottom;