clang-cl: Support /showIncludes

This option prints information about #included files to stderr. Clang could
already do it, this patch just teaches the existing code about the /showIncludes
style and adds the flag.

Differential Revision: http://llvm-reviews.chandlerc.com/D1333

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@188037 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Frontend/print-header-includes.c b/test/Frontend/print-header-includes.c
index 7773d20..aa3e397 100644
--- a/test/Frontend/print-header-includes.c
+++ b/test/Frontend/print-header-includes.c
@@ -5,4 +5,11 @@
 // CHECK: . {{.*test.h}}
 // CHECK: .. {{.*test2.h}}
 
+// RUN: %clang_cc1 -include Inputs/test3.h -E --show-includes -o %t.out %s 2> %t.err
+// RUN: FileCheck --check-prefix=MS < %t.err %s
+// MS-NOT: test3.h
+// MS: Note: including file: {{.*test.h}}
+// MS: Note: including file:  {{.*test2.h}}
+// MS-NOT: Note
+
 #include "Inputs/test.h"