MachO: actually set linker-private prefix at MC level.

This was accidentally omitted from r205081.

llvm-svn: 205083

Author: TNorthover

llvm/lib/MC/MCAsmInfoDarwin.cpp

@@ -23,6 +23,7 @@ void MCAsmInfoDarwin::anchor() { }
 MCAsmInfoDarwin::MCAsmInfoDarwin() {
   // Common settings for all Darwin targets.
   // Syntax:
+  LinkerPrivateGlobalPrefix = "l";
   HasSingleParameterDotFile = false;
   HasSubsectionsViaSymbols = true;