glib2.0 causing some build errors in Hirsute

[Christian Ehrhardt]

Hi,
this is an FYI in case other packages FTBFS as well (in my case qemu)
in Hirsute-proposed.
There is a change in libglib2.0-dev 2.66.4-1 to 2.67.4-1 which makes
it break build if it is included in an "extern C" context.

That is discussed upstream  https://gitlab.gnome.org/GNOME/glib/-/issues/233
The TL;DR is no mitigation will be applied, but in turn that means we
need to fix all problematic packages in Hirsute to avoid becoming an
FTBFS.

Remember this case if you see build issues like:

../../disas/arm-a64.cc
In file included from /usr/include/glib-2.0/glib/gmacros.h:241,
                 from /usr/lib/x86_64-linux-gnu/glib-2.0/include/glibconfig.h:9,
                 from /usr/include/glib-2.0/glib/gtypes.h:32,
                 from /usr/include/glib-2.0/glib/galloca.h:32,
                 from /usr/include/glib-2.0/glib.h:30,
                 from /<<BUILDDIR>>/qemu-5.2+dfsg/include/glib-compat.h:32,
                 from /<<BUILDDIR>>/qemu-5.2+dfsg/include/qemu/osdep.h:126,
                 from ../../disas/arm-a64.cc:21:
/usr/include/c++/10/type_traits:56:3: error: template with C linkage
   56 |   template<typename _Tp, _Tp __v>
      |   ^~~~~~~~
../../disas/arm-a64.cc:20:1: note: ‘extern "C"’ linkage started here
   20 | extern "C" {
      | ^~~~~~~~~~

Thanks Doko for debugging with me and Laney to point to the upstream issue.

-- 
Christian Ehrhardt
Staff Engineer, Ubuntu Server
Canonical Ltd