glib: Work around AppleClang + -Werror test build failure

Hi,

This MR is to work around an error I found with Xcode 13.2.1 when building glib. The error comes from using function prototypes that are conditionally defined, and this one in particular isn't included in the test preamble. That is not allowed, and is enforced by the combination of -std=gnu99 and -Werror.

See: https://gitlab.gnome.org/GNOME/glib/-/issues/2902

mentioned in merge request !1255 (merged)

assigned to @gstreamer-merge-bot

added 1.22 Needs backport labels

mentioned in commit amyspark/cerbero@1051cb94

added 25 commits

• a0cdba2e...139645b8 - 24 commits from branch gstreamer:main
• 1051cb94 - glib: Work around AppleClang + -werror test build failure

Compare with previous version

merged

changed milestone to %1.23.1

added Backported into 1.22 label and removed Needs backport label

Merge Request for backport into 1.22 branch: !1294 (merged) (target milestone: 1.22.7)

Needs manual intervention!

mentioned in merge request !1294 (merged)

mentioned in commit tpm/cerbero@f2903e37