Don't emit throw types at -gline-tables-only.

Caught by the debug-stdlib bots.

rdar://105651154

Author: adrian-prantl

lib/IRGen/IRGenDebugInfo.cpp

@@ -2416,7 +2416,7 @@ IRGenDebugInfoImpl::emitFunction(const SILDebugScope *DS, llvm::Function *Fn,
 
   // Get the throws information.
   llvm::DITypeArray Error = nullptr;
-  if (FnTy)
+  if (FnTy && (Opts.DebugInfoLevel > IRGenDebugInfoLevel::LineTables))
     if (auto ErrorInfo = FnTy->getOptionalErrorResult()) {
       SILType SILTy = IGM.silConv.getSILType(
           *ErrorInfo, FnTy, IGM.getMaximalTypeExpansionContext());