Don't refer to optarg in dwarf.c function

[Alan Modra]

This one is passed in optarg as its argument.

	PR binutils/17926
	* dwarf.c (dwarf_select_sections_by_letters): Don't refer to optarg.

diff --git a/binutils/dwarf.c b/binutils/dwarf.c
index b65bb7b..aa19725 100644
--- a/binutils/dwarf.c
+++ b/binutils/dwarf.c
@@ -7414,7 +7414,7 @@ dwarf_select_sections_by_letters (const char *letters)
 	break;
 
       default:
-	warn (_("Unrecognized debug option '%s'\n"), optarg);
+	warn (_("Unrecognized debug option '%s'\n"), letters);
 	break;
       }
 }

-- 
Alan Modra
Australia Development Lab, IBM