Add experimental options for call site related dbg info

[djtodoro]

Summary

Set the backend option for emitting DW_OP_entry_values to true if '-femit-param-entry-values' is invoked.

In addition, set up as well a MIR option that enables emitting info about call site parameter's forwarding regs.

Authors: @asowda, @NikolaPrica, @djtodoro, @ivanbaev

[djtodoro]

-Rebase

[djtodoro]

-Rebase

lib/Driver/ToolChains/Clang.cpp

if (DebuggerTuning == llvm::DebuggerKind::SCE)
     CmdArgs.push_back("-debug-forward-template-params");
 
   // Do we need to explicitly import anonymous namespaces into the parent
   // scope?
   if (DebuggerTuning == llvm::DebuggerKind::SCE)
     CmdArgs.push_back("-dwarf-explicit-import");
 
   // Enable param entry values functionlaity.
-  if (Args.hasArg(options::OPT_emit_param_entry_values))
+  if (Args.hasArg(options::OPT_emit_param_entry_values)) {
     CmdArgs.push_back("-emit-param-entry-values-cc1");
+    CmdArgs.push_back("-mllvm");
+    CmdArgs.push_back("-emit-entry-values=1");
+  }
 
   RenderDebugInfoCompressionArgs(Args, CmdArgs, D, TC);
 }
 
 void Clang::ConstructJob(Compilation &C, const JobAction &JA,
                          const InputInfo &Output, const InputInfoList &Inputs,
                          const ArgList &Args, const char *LinkingOutput) const {
   const auto &TC = getToolChain();