[Swan] dependencies in Makefiles

[D. Hugh Redelmeier]

How are dependencies updated for libreswan's Makefiles?

A decade ago, I had a crude mechanism to update the dependencies in 
Pluto's makefile.  A little bit of that is still in 
programs/pluto/Makefile, but it is broken.

Currently the dependencies are wrong and I don't know how to update them.

Perhaps these files are relevant.  But something's wrong: 0 isn't a 
reasonable size.

$ du -a | grep depend
0       ./programs/pluto/Makefile.depend.linux
60      ./programs/pluto/Makefile.depend.freebsd
4       ./testing/crypto/psk-v2-10/Makefile.depend
4       ./testing/crypto/rsa-v2-08/Makefile.depend
0       ./testing/lib/libpluto/Makefile.depend.linux
8       ./lib/libipsecconf/Makefile.depend.linux
24      ./lib/libswan/Makefile.depend