Correct setting of UserLabelPrefix for MCU target.

Differential Revision: http://reviews.llvm.org/D16138

llvm-svn: 257756
diff --git a/clang/lib/Basic/Targets.cpp b/clang/lib/Basic/Targets.cpp
index 1bc6c51..4bb77a0 100644
--- a/clang/lib/Basic/Targets.cpp
+++ b/clang/lib/Basic/Targets.cpp
@@ -3899,6 +3899,7 @@
   MCUX86_32TargetInfo(const llvm::Triple &Triple) : X86_32TargetInfo(Triple) {
     LongDoubleWidth = 64;
     LongDoubleFormat = &llvm::APFloat::IEEEdouble;
+    UserLabelPrefix = "";
   }
 
   CallingConvCheckResult checkCallingConvention(CallingConv CC) const override {