[asan] Change the visibility of ___asan_globals_registered to hidden

This flag is used to track global registration in Mach-O and it doesn't need to be exported and visible.

Differential Revision: https://reviews.llvm.org/D28250

llvm-svn: 291289

llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp

@@ -1818,6 +1818,7 @@ bool AddressSanitizerModule::InstrumentGlobals(IRBuilder<> &IRB, Module &M) {
     RegisteredFlag = new GlobalVariable(
         M, IntptrTy, false, GlobalVariable::CommonLinkage,
         ConstantInt::get(IntptrTy, 0), kAsanGlobalsRegisteredFlagName);
+    RegisteredFlag->setVisibility(GlobalVariable::HiddenVisibility);
 
     // Update llvm.compiler.used, adding the new liveness globals. This is
     // needed so that during LTO these variables stay alive. The alternative