How to generate a Makefile.depend?

I'm trying to add a little tool to my local tree and I'm stuck with
something I *assume* should be simple. As I understand it, there should
be a Makefile.depend in its directory, listing all the dir dependencies,
and this should be somehow auto-generated from .meta files. I just can't
figure out how to do it.

I have this very simple Makefile for it:
---
# $FreeBSD$

PACKAGE=	runtime

PROG=	pam_unix-helper
MAN=	# no manpage, internally used by pam_unix.so

LIBADD=	crypt

BINOWN=	root
BINMODE=4555

.include <bsd.prog.mk>
---

It builds just fine (using meta mode), so what do I need to do to get
the corresponding Makefile.depend?

TIA, Felix

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