[ELF2] Implement support for -discard-locals.

This is not on by default, but it may make sense to change it in future.

llvm-svn: 248133
diff --git a/lld/ELF/Driver.cpp b/lld/ELF/Driver.cpp
index 8328ba5..6537e13 100644
--- a/lld/ELF/Driver.cpp
+++ b/lld/ELF/Driver.cpp
@@ -85,6 +85,9 @@
   if (Args.hasArg(OPT_discard_all))
     Config->DiscardAll = true;
 
+  if (Args.hasArg(OPT_discard_locals))
+    Config->DiscardLocals = true;
+
   // Create a list of input files.
   std::vector<MemoryBufferRef> Inputs;