Update OptionGroup::SetValue to take StringRef.

Then deal with all the fallout.

Differential Revision: https://reviews.llvm.org/D24847

llvm-svn: 282265
diff --git a/lldb/source/Interpreter/Options.cpp b/lldb/source/Interpreter/Options.cpp
index 8b28c6d..f8eadcc 100644
--- a/lldb/source/Interpreter/Options.cpp
+++ b/lldb/source/Interpreter/Options.cpp
@@ -913,8 +913,8 @@
   Error error;
   if (option_idx < m_option_infos.size()) {
     error = m_option_infos[option_idx].option_group->SetOptionValue(
-        m_option_infos[option_idx].option_index, option_value,
-        execution_context);
+        m_option_infos[option_idx].option_index,
+        llvm::StringRef::withNullAsEmpty(option_value), execution_context);
 
   } else {
     error.SetErrorString("invalid option index"); // Shouldn't happen...