Don't report memory return values on MacOS_arm64 of SysV_arm64 ABI's.

They don't require that the memory return address be restored prior to
function exit, so there's no guarantee the value is correct.  It's better
to return nothing that something that's not accurate.

Differential Revision: https://reviews.llvm.org/D121348

lldb/source/API/SBTarget.cpp

@@ -1588,6 +1588,18 @@ const char *SBTarget::GetTriple() {
   return nullptr;
 }
 
+const char *SBTarget::GetABIName() {
+  LLDB_INSTRUMENT_VA(this);
+  
+  TargetSP target_sp(GetSP());
+  if (target_sp) {
+    std::string abi_name(target_sp->GetABIName().str());
+    ConstString const_name(abi_name.c_str());
+    return const_name.GetCString();
+  }
+  return nullptr;
+}
+
 uint32_t SBTarget::GetDataByteSize() {
   LLDB_INSTRUMENT_VA(this);