Fixed failure on Darwin due to r354064

[apazos]

Summary

instrprof-darwin-exports.c test fails on Darwin due to r354064.

Updated clang list of exported symbols to fix the issue.

[vsk]

Thanks, lgtm.

lib/Driver/ToolChains/Darwin.cpp

if (hasExportSymbolDirective(Args)) {
     if (needsGCovInstrumentation(Args)) {
       addExportedSymbol(CmdArgs, "___gcov_flush");
       addExportedSymbol(CmdArgs, "_flush_fn_list");
       addExportedSymbol(CmdArgs, "_writeout_fn_list");
     } else {
       addExportedSymbol(CmdArgs, "___llvm_profile_filename");
       addExportedSymbol(CmdArgs, "___llvm_profile_raw_version");
       addExportedSymbol(CmdArgs, "_lprofCurFilename");
-      addExportedSymbol(CmdArgs, "_lprofMergeValueProfData");
     }
     addExportedSymbol(CmdArgs, "_lprofDirMode");
   }
 }
 
 void DarwinClang::AddLinkSanitizerLibArgs(const ArgList &Args,
                                           ArgStringList &CmdArgs,
                                           StringRef Sanitizer,