bug#47159: 28.0.50; gnutls not recognized in build process without pkg-config

[Lars Ingebrigtsen <larsi@gnus.org>]

Jean Louis <bugs@gnu.support> writes:

> Emacs' configure was complaining that gnutls cannot be found. But it was
> there.
>
> By chance I was thinkin that build process maybe uses pkg-config, so I
> have installed pkg-config as package. The build process then continued
> and could find gnutls.

I can reproduce this on Debian/bullseye, too.  I removed pkg-config and
ran ./configure.  It says:

configure: error: The following required libraries were not found:
     libtiff gnutls
Maybe some development libraries/packages are missing?
To build anyway, give:
     --with-tiff=ifavailable --with-gnutls=ifavailable
as options to configure.

"sudo apt install pkg-config" and then ./configure
--with-tiff=ifavailable allowed me to build Emacs.

I can't see any explicit checks for pkg-config in configure.ac.

I'm wondering whether this is a packaging error.  Most of the other
devel packages depend on pkg-config, so it'll be pulled in automatically
(which is probably why this hasn't been an issue before).  But
gnutls-dev does not depend on pkg-config.

So I guess we should just add a check for pkg-config in the gnutls
check?  Any opinions?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no