host-mkdep(1): Add support for -iquote.

Not used yet, but may eventually replace deprecated -I-, both for
GCC and clang.

tools/host-mkdep/host-mkdep.in

@@ -1,6 +1,6 @@
 #!@BSHELL@ -
 #
-#	$NetBSD: host-mkdep.in,v 1.32 2019/10/29 23:33:06 joerg Exp $
+#	$NetBSD: host-mkdep.in,v 1.33 2023/07/10 08:55:44 rin Exp $
 #
 # Copyright (c) 1991, 1993
 #	The Regents of the University of California.  All rights reserved.
@@ -151,7 +151,7 @@ else
 				cppargs=${cppargs%x}
 				;;
 
-		-[IDU]|-include|-isystem|-isysroot)
+		-[IDU]|-include|-iquote|-isystem|-isysroot)
 				set -- "$@" "$1" "$2"
 				shift 2
 				cppargs=${cppargs%xx}