Use -disable-output and to suppress output and don't use a temporary file unless we need one.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188843 91177308-0d34-0410-b5e6-96231b3b80d8

test/Bitcode/metadata.ll

@@ -1,6 +1,5 @@
-; RUN: llvm-as < %s | llvm-dis -o /dev/null
+; RUN: llvm-as < %s | llvm-dis -disable-output
 
 !llvm.foo = !{!0}
 !0 = metadata !{i32 42}
 @my.str = internal constant [4 x i8] c"foo\00"
-