Bug#1017578: gtk+3.0: build test failures with glib 2.73

[Jeremy Bicha]

Source: gtk+3.0
Version: 3.24.34-1
Severity: important

As detected by autopkgtests, gtk+3.0 will fail its build tests with
glib 2.73 (currently in experimental).

We need to adapt https://gitlab.gnome.org/GNOME/gtk/-/commit/78c153ae14
for the older code base.

TEST: icontheme... (pid=3486770)
  /icontheme/basics:                                                   OK
  /icontheme/lookup-order:
(/<<PKGBUILDDIR>>/debian/build/deb/testsuite/gtk/.libs/icontheme:3486770):
GLib-ERROR **: 22:37:08.353: g_log_set_writer_func() called multiple
times
FAIL
GTester: last random seed: R02S6d667302897b32fd5f67396760fbaa55
(pid=3486785)
  /icontheme/generic-fallback:                                         OK
  /icontheme/force-symbolic:                                           OK
  /icontheme/force-regular:                                            OK
  /icontheme/rtl:                                                      OK
  /icontheme/symbolic-single-size:                                     OK
  /icontheme/svg-size:                                                 OK
  /icontheme/size:                                                     OK
  /icontheme/builtin:                                                  OK
  /icontheme/list:                                                     OK
  /icontheme/async:                                                    OK
  /icontheme/inherit:                                                  OK
  /icontheme/nonsquare-symbolic:                                       OK
FAIL: icontheme

Thank you,
Jeremy Bicha