Reduce temp file pollution in some test cases.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@161237 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Driver/warning-options.cpp b/test/Driver/warning-options.cpp
index ce434ab..ab0da42 100644
--- a/test/Driver/warning-options.cpp
+++ b/test/Driver/warning-options.cpp
@@ -3,7 +3,7 @@
 // RUN: %clang -### -Wlarge-by-value-copy=128 %s 2>&1 | FileCheck -check-prefix=LARGE_VALUE_COPY_JOINED %s
 // LARGE_VALUE_COPY_JOINED: -Wlarge-by-value-copy=128
 
-// RUN: %clang -c -Wmonkey -Wno-monkey -Wno-unused-command-line-arguments \
+// RUN: %clang -### -c -Wmonkey -Wno-monkey -Wno-unused-command-line-arguments \
 // RUN:        -Wno-unused-command-line-argument %s 2>&1 | FileCheck %s
 // CHECK: unknown warning option '-Wmonkey'
 // CHECK: unknown warning option '-Wno-monkey'