Lazy dependencies are only fetched if the build script would actually
reach a usage of that dependency at runtime (when the `lazyDependency`
function is called). This can save a lot of network traffic, disk uage,
and time because we don't have to fetch and build dependencies that we
don't actually need.
Prior to this commit, Ghostty fetched almost everything for all
platforms and configurations all the time. This commit reverses that to
fetching almost nothing until it's actually needed.
There are very little downsides to doing this[1]. One downside is `zig
build --fetch` doesn't fetch lazy dependencies, but we don't rely on
this command for packaging and suggest using our custom shell script
that downloads a cached list of URLs (`build.zig.zon.txt`).
This commit doesn't cover 100% of dependencies, since some provide no
benefit to make lazy while the complexity to make them lazy is higher
(in code style typically).
Conversely, some simple dependencies are marked lazy even if they're
almost always needed if they don't introduce any real complexity to the
code, because there is very little downside to do so.
[1]: https://ziggit.dev/t/lazy-dependencies-best-dependencies/5509/5
As of now `gtk4-layer-shell` is unavailable on recent, stable releases
of many distros (Debian 12, Ubuntu 24.04, openSUSE Leap & Tumbleweed, etc.)
and outdated on many others (Nixpkgs 24.11/unstable, Fedora 41, etc.)
This is inconvenient for our users and severely limits where the quick
terminal can be used. As a result we then build gtk4-layer-shell ourselves
by default unless `--system` or `-fsys=gtk4-layer-shell` are specified.
This also allows me to add an idiomatic Zig API on top of the library
and avoiding adding even more raw C code in the GTK apprt.
Since we now build gtk4-layer-shell it should be theoretically available
on all Linux systems we target. As such, the `-Dgtk-layer-shell` build
option has been removed. This is somewhat of an experimental change as
I don't know if gtk4-layer-shell works perfectly across all distros, and
we can always add the option back if need be.
