The AUR is for Arch and trying to use it on a different distro will have mixed results at best.
You can either wait for Manjaro to catch up and add the glib2-devel package which was created over a month ago, or edit the plgbuild and change it to glib2
I’ve done this!
Turn the shower on just high enough to get a good mist going then put a box fan on high as close as possible pointing out of the bathroom.