Hi Ludovic,

> It seems to me that we shouldn’t provide .pc files if upstream doesn’t
> do it.  The main reason is that developers who use Guix will come to
> rely on it and unknowingly write code that doesn’t work on other
> distros.  (I remember pestering in the past as I stumbled upon packages
> who depended on some library as packaged by a specific distro.  :-))
> 
> WDYT?
> 
> Apologies if I missed an earlier discussion!

No apologies needed, the discussion was minimal at best.  This patch is the
result of my yielding to the forces of incompatibility you mention.  Major
distributions like Debian, Arch Linux [1], and Fedora [2] have all added pkg-
config files for (at least) libmad.  Audacity expects to find pkg-config files
for the system libraries it uses, so I supplied those to follow the path of
least resistance.

If there's a way to supply "-I" and "-L" flags directly somewhere in the build
process as was done before, I'm not opposed to reverting these changes and
modifying Audacity's package definition myself during the next update.  I'll
investigate some of our other CMake packages for possible inspiration.

Thanks,
Kei

[0]: https://packages.debian.org/buster/amd64/libmad0-dev/filelist
[1]: 
https://github.com/archlinux/svntogit-packages/blob/packages/libmad/trunk/libmad.patch
[2]: 
https://koji.fedoraproject.org/koji/rpminfo?fileOrder=-name&rpmID=22388610&buildrootOrder=-id&buildrootStart=0#filelist