deps: Default gtk4-layer-shell system integration to true

We default system-integration to true as this is a shared library that
must be installed on a library path and it is recommended to use the
system package.

If the system does not package gtk4-layer-shell then doing `zig build
-fno-sys` will now correctly build and install the shared library under
a lib/ subdirectory of the output prefix.

The output prefix should be a default library path (`/lib`, `/usr/lib`,
or a lib64 variant) otherwise a custom library path can be configured
using ldconfig (see `man ld.so 8`)

src/build/Config.zig

@@ -361,7 +361,6 @@ pub fn init(b: *std.Build) !Config {
             "libpng",
             "zlib",
             "oniguruma",
-            "gtk4-layer-shell",
         }) |dep| {
             _ = b.systemIntegrationOption(
                 dep,
@@ -387,6 +386,15 @@ pub fn init(b: *std.Build) !Config {
         }) |dep| {
             _ = b.systemIntegrationOption(dep, .{ .default = false });
         }
+
+        // These are dynamic libraries we default to true, preferring
+        // to use system packages over building and installing libs
+        // as they require additional ldconfig of library paths or
+        // patching the rpath of the program to discover the dynamic library
+        // at runtime
+        for (&[_][]const u8{"gtk4-layer-shell"}) |dep| {
+            _ = b.systemIntegrationOption(dep, .{ .default = true });
+        }
     }
 
     return config;

src/build/SharedDeps.zig

@@ -652,14 +652,13 @@ fn addGTK(
             // IMPORTANT: gtk4-layer-shell must be linked BEFORE
             // wayland-client, as it relies on shimming libwayland's APIs.
             if (b.systemIntegrationOption("gtk4-layer-shell", .{})) {
-                step.linkSystemLibrary2(
+                step.linkSystemLibrary2("gtk4-layer-shell-0", dynamic_link_opts);
-                    "gtk4-layer-shell-0",
-                    dynamic_link_opts,
-                );
             } else {
                 // gtk4-layer-shell *must* be dynamically linked,
                 // so we don't add it as a static library
-                step.linkLibrary(gtk4_layer_shell.artifact("gtk4-layer-shell"));
+                const shared_lib = gtk4_layer_shell.artifact("gtk4-layer-shell");
+                b.installArtifact(shared_lib);
+                step.linkLibrary(shared_lib);
             }
         }