gplugin/gplugin

Add gir targets to the dependencies sources attribute and other meson cleanups.

2021-09-25, Gary Kramlich
476c9cac712b
Add gir targets to the dependencies sources attribute and other meson cleanups.

Adding the gir targs to the dependency object of the library allows us to be
able to use the dependency in a gnome.generate_gir for a library that consumes
our api regardless of if it's a system install or a subproject.

Testing Done:
Modified the gplugin subproject in pidgin and used these changes to verify that it fixed the current build issues over there.

Reviewed at https://reviews.imfreedom.org/r/939/
# Dependencies
GPlugin depends on the following at a bare minimum:
* glib-2.0 >= 2.40.0
* gobject-introspection, libgirepository1.0-dev
* meson >= 0.42.0
* gettext
* help2man
* a C compiler
A full build (enabled by default) depends on the following:
* gtk-3
* python3-dev, python-gi-dev, python3-gi
* libperl-dev, libglib-perl, libglib-object-introspection-perl
* liblua5.1-0-dev, lua-lgi
* valac
All of these packages and their development headers need to be installed
prior to building GPlugin.
# Building
GPlugin uses [meson](https://mesonbuild.com/) as its build system. As such
compiling is a little bit different than your typical `./configure`, `make`,
`sudo make install`.
Meson requires you to build in a separate directory than your source. As such,
these instructions use a separate build directory.
To compile you need to run the following commands:
```
meson build
cd build
ninja install
```
If you want/need to tweak the build system (to enable/disable certain loaders)
you can do so at any time by using `meson configure` in the build directory.