llvm-mc: Use Target::createNullStreamer to fix crashes on target-specific asm directives.

llvm-svn: 229798
diff --git a/llvm/test/CodeGen/ARM/null-streamer.ll b/llvm/test/CodeGen/ARM/null-streamer.ll
index 350c45e..19ad22a 100644
--- a/llvm/test/CodeGen/ARM/null-streamer.ll
+++ b/llvm/test/CodeGen/ARM/null-streamer.ll
@@ -5,3 +5,5 @@
 entry:
   ret i32 0
 }
+
+module asm ".fnstart"