Use -flto instead of -flto=N in DWARF producer string.

2019-07-23  Martin Liska  <mliska@suse.cz>

	* dwarf2out.c (gen_producer_string): Canonize -flto=N
	to -flto in dwarf producer string.

From-SVN: r273717

gcc/ChangeLog

+2019-07-23  Martin Liska  <mliska@suse.cz>
+
+	* dwarf2out.c (gen_producer_string): Canonize -flto=N
+	to -flto in dwarf producer string.
+
 2019-07-23  Richard Biener  <rguenther@suse.de>
 
 	* tree-cfg.c (label_for_bb): Remove global var.

gcc/dwarf2out.c

@@ -24460,6 +24460,13 @@ gen_producer_string (void)
       case OPT_fchecking_:
 	/* Ignore these.  */
 	continue;
+      case OPT_flto_:
+	{
+	  const char *lto_canonical = "-flto";
+	  switches.safe_push (lto_canonical);
+	  len += strlen (lto_canonical) + 1;
+	  break;
+	}
       default:
         if (cl_options[save_decoded_options[j].opt_index].flags
 	    & CL_NO_DWARF_RECORD)