Bug#842529: pkgconf Provides: pkg-config without supplying the full interface: missing cross wrapper symlinks

[Helmut Grohne <helmut@subdivi.de>]

Package: pkgconf
Version: 0.9.12-1
User: helmutg@debian.org
Usertags: rebootstrap

I noticed that pkgconf provides and diverts pkg-config without supplying
its full interface. Notable differences:
 1. pkg-config ensures that /usr/bin/$DEB_HOST_GNU_TYPE-pkg-config works
    for every architecture added via dpkg --add-architecture.
 2. pkg-config is Multi-Arch: foreign while pkgconf is not (and cannot
    due to 1).

Due to these differences, cross builds involving pkg-config fail when
their pkg-config dependency is satisfied with pkgconf. The typical
symptoms are that /usr/bin/$DEB_HOST_GNU_TYPE-pkg-config cannot be found
and dependencies detected as missing.

I'm unsure how to proceed here. One solution could be depending on
pkg-config to have it instate those symlinks. That seems strange when
pkgconf is supposed to replace pkg-config.

Then, it could add its own management of the symlinks. pkg-config uses
/usr/share/pkg-config-dpkghook to create, update and remove them. It is
not clear to me what happens when two packages manage them, so possibly
pkgconf may have to declare Breaks: pkg-config.

Given that I have no good idea on how to resolve the issue, I am merely
reporting it and hoping that others chime in.

Helmut