bug#18247: Cyclic dependencies in (gnu package *) modules

[mhw]

I'm currently unable to compile guix from git, with error messages that
suggest cyclic dependencies between the modules.  I just computed the
strongly connected components of the (gnu package *) modules.  The
non-trivial ones are listed below.

There are three cycles of size 2:

((gnu packages emacs)  (gnu packages version-control))
((gnu packages flex)   (gnu packages bison))
((gnu packages python) (gnu packages zip))

And one large strongly-connected component containing 51 modules:

((gnu packages acl)
 (gnu packages gettext)
 (gnu packages xml)
 (gnu packages linux)
 (gnu packages gtk)
 (gnu packages xorg)
 (gnu packages gnupg)
 (gnu packages glib)
 (gnu packages base)
 (gnu packages texinfo)
 (gnu packages gcc)
 (gnu packages openldap)
 (gnu packages groff)
 (gnu packages netpbm)
 (gnu packages ghostscript)
 (gnu packages tcl)
 (gnu packages fontutils)
 (gnu packages cyrus-sasl)
 (gnu packages mit-krb5)
 (gnu packages curl)
 (gnu packages ssh)
 (gnu packages gsasl)
 (gnu packages shishi)
 (gnu packages gnutls)
 (gnu packages gl)
 (gnu packages pdf)
 (gnu packages lesstif)
 (gnu packages gnome)
 (gnu packages libcanberra)
 (gnu packages xiph)
 (gnu packages pulseaudio)
 (gnu packages web)
 (gnu packages docbook)
 (gnu packages avahi)
 (gnu packages algebra)
 (gnu packages mpi)
 (gnu packages valgrind)
 (gnu packages gdb)
 (gnu packages dejagnu)
 (gnu packages doxygen)
 (gnu packages graphviz)
 (gnu packages gd)
 (gnu packages gstreamer)
 (gnu packages iso-codes)
 (gnu packages rrdtool)
 (gnu packages maths)
 (gnu packages texlive)
 (gnu packages tcsh)
 (gnu packages lisp)
 (gnu packages fltk)
 (gnu packages attr))

     Mark