[LTO] Discard names for Values that are not global.

This is not on by default (but it might be in the future).
The knob to enable the optimization is -lto-discard-value-names.

llvm-svn: 266953
diff --git a/lld/ELF/Driver.cpp b/lld/ELF/Driver.cpp
index f72fa3d..dc49530 100644
--- a/lld/ELF/Driver.cpp
+++ b/lld/ELF/Driver.cpp
@@ -289,6 +289,7 @@
   Config->Demangle = !Args.hasArg(OPT_no_demangle);
   Config->DisableVerify = Args.hasArg(OPT_disable_verify);
   Config->DiscardAll = Args.hasArg(OPT_discard_all);
+  Config->DiscardValueNames = Args.hasArg(OPT_lto_discard_value_names);
   Config->DiscardLocals = Args.hasArg(OPT_discard_locals);
   Config->DiscardNone = Args.hasArg(OPT_discard_none);
   Config->EhFrameHdr = Args.hasArg(OPT_eh_frame_hdr);