Define --output= as an alias to -o.

llvm-svn: 249789
diff --git a/lld/ELF/Driver.cpp b/lld/ELF/Driver.cpp
index 2ae38c9..b4395e8 100644
--- a/lld/ELF/Driver.cpp
+++ b/lld/ELF/Driver.cpp
@@ -188,7 +188,7 @@
   Config->Entry = getString(Args, OPT_entry);
   Config->Fini = getString(Args, OPT_fini, "_fini");
   Config->Init = getString(Args, OPT_init, "_init");
-  Config->OutputFile = getString(Args, OPT_output);
+  Config->OutputFile = getString(Args, OPT_o);
   Config->SoName = getString(Args, OPT_soname);
   Config->Sysroot = getString(Args, OPT_sysroot);