gplugin/gplugin

Make sure gtk4 was found before trying to build vala bindings against it
default tip
8 days ago, Gary Kramlich
7027845d098d
Make sure gtk4 was found before trying to build vala bindings against it

This error only showed up when gtk4 was enabled but not found.

Testing Done:
Built on haiku that doesn't have gtk without setting `-Dgtk4=false`.
Built on debian testing normally.

Reviewed at https://reviews.imfreedom.org/r/3069/
# GPlugin
[ ![Download](https://api.bintray.com/packages/pidgin/releases/GPlugin/images/download.svg) ](https://bintray.com/pidgin/releases/GPlugin/_latestVersion)
[ ![Issues](https://img.shields.io/badge/Issues-YouTrack-ee3b8b.svg) ](https://issues.imfreedom.org/issues/GPLUGIN)
GPlugin is a GObject based library that implements a reusable plugin system.
It supports loading plugins in multiple other languages via loaders. It relies
heavily on [GObjectIntrospection](https://gi.readthedocs.io/) to expose its API
to the other languages.
It has a simple API which makes it very easy to use in your application.
For more information on using GPlugin in your application, please see the
[embedding](https://docs.pidgin.im/gplugin/latest/chapter-embedding.html) page.
## History
GPlugin has a bit of history, you can read more about it in
[HISTORY.md](HISTORY.md)
## Language Support
GPlugin currently supports plugins written in C/C++, Lua, Python3, and Vala.
## API Reference
The in-development API reference for the development branch can be found at
[docs.imfreedom.org/gplugin/](https://docs.imfreedom.org/gplugin/) for the core
library and
[docs.imfreedom.org/gplugin-gtk4/](https://docs.imfreedom.org/gplugin-gtk4/) for
the GTK4 integration.