Driver: Fix a -Wshadow issue from r237091

The MachO toolchain has an isTargetIOSBased method, but it isn't
virtual so it isn't very meaningful to call it. After thinking about
this, I guess that putting this logic in the MachO class is a bit of a
layering violation anyway. Do this more like how we handle
AddLinkRuntimeLibArgs instead.

llvm-svn: 237095
diff --git a/clang/lib/Driver/ToolChains.cpp b/clang/lib/Driver/ToolChains.cpp
index 4ecd9a9..5428a55 100644
--- a/clang/lib/Driver/ToolChains.cpp
+++ b/clang/lib/Driver/ToolChains.cpp
@@ -326,7 +326,7 @@
   }
 }
 
-void MachO::addProfileRTLibs(const ArgList &Args,
+void Darwin::addProfileRTLibs(const ArgList &Args,
                              ArgStringList &CmdArgs) const {
   if (!(Args.hasFlag(options::OPT_fprofile_arcs, options::OPT_fno_profile_arcs,
                      false) ||