ci: Add wrap file for libglib-testing

This is needed for building malcontent as a subproject; currently, Meson
doesn’t support recursively downloading the subprojects for nested wrap
files. (See https://github.com/mesonbuild/meson/issues/1489.) So we need
to provide `libglib-testing.wrap` in the top-level subprojects directory
in order for the `cache-subprojects.sh` script to correctly cache it in
the Docker images for CI.

This also requires bumping the malcontent dependency so that we pull in
a version of malcontent which uses the subproject.

Signed-off-by: Philip Withnall <withnall@endlessm.com>
10 jobs for sysprof-4-followup in 7 minutes and 40 seconds
Status Job ID Name Coverage
  Build
passed #802382
debian-stable-x86_64

00:02:13

failed #802396
fedora-x86_64

00:05:26

canceled #800443
debian-stable-x86_64

00:00:17

failed #800577
debian-stable-x86_64

00:03:13

failed #800575
debian-stable-x86_64

00:02:41

failed #800453
debian-stable-x86_64

00:02:41

failed #800616
debian-stable-x86_64

00:00:58

failed #800454
fedora-x86_64

00:00:35

canceled #800442
fedora-x86_64

00:00:17

failed #802395
fedora-x86_64

00:06:28

 
Name Stage Failure
failed
fedora-x86_64 Build
Uploading artifacts...
_build/config.h: found 1 matching files

_build/meson-logs: found 4 matching files

_build/fedora-x86_64-report.xml: found 1 matching files

Uploading artifacts to coordinator... ok
id=802396 responseStatus=201 Created token=NQ_uNMJH
Uploading artifacts...
_build/fedora-x86_64-report.xml: found 1 matching files

Uploading artifacts to coordinator... ok
id=802396 responseStatus=201 Created token=NQ_uNMJH
ERROR: Job failed: exit code 1