Default systemIntegrationOption for gtk4-layer-shell to true

- Add an absolute rpath entry in Debug mode only to test gtk4-layer-shell when not
  using the system package
  * Prefer using ldconfig to discover installed libs in custom prefixes

Fix variable name cases

Author: AnthonyZhOon

src/build/Config.zig

@@ -337,8 +337,8 @@ pub fn init(b: *std.Build) !Config {
         target.result.os.tag == .macos and
         config.app_runtime == .none and
         (!config.emit_bench and
-            !config.emit_test_exe and
-            !config.emit_helpgen);
+        !config.emit_test_exe and
+        !config.emit_helpgen);
 
     //---------------------------------------------------------------
     // System Packages
@@ -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

@@ -14,7 +14,6 @@ help_strings: HelpStrings,
 metallib: ?*MetallibStep,
 unicode_tables: UnicodeTables,
 framedata: GhosttyFrameData,
-steps: []*std.Build.Step,
 
 /// Used to keep track of a list of file sources.
 pub const LazyPathList = std.ArrayList(std.Build.LazyPath);
@@ -649,12 +648,19 @@ fn addGTK(
             } else {
                 // gtk4-layer-shell *must* be dynamically linked,
                 // so we don't add it as a static library
-                const sharedLib = gtk4_layer_shell.artifact("gtk4-layer-shell");
-                const artifact: *std.Build.Step.InstallArtifact = b.addInstallArtifact(sharedLib, .{});
+                const shared_lib = gtk4_layer_shell.artifact("gtk4-layer-shell");
+                const artifact: *std.Build.Step.InstallArtifact = b.addInstallArtifact(shared_lib, .{});
                 b.getInstallStep().dependOn(&artifact.step);
-                // Lookup dynamic libs from installed location
-                step.root_module.addRPathSpecial(b.getInstallPath(artifact.dest_dir.?, ""));
-                step.linkLibrary(sharedLib);
+                step.linkLibrary(shared_lib);
+                if (self.config.optimize == .Debug) {
+                    // Lookup dynamic libs from installed location
+                    const install_path = b.getInstallPath(artifact.dest_dir.?, "");
+                    if (!std.fs.path.isAbsolute(install_path)) {
+                        // Using a relative path as an rpath is almost useless
+                        return error.UndesirableRelativePath;
+                    }
+                    step.root_module.addRPathSpecial(install_path);
+                }
             }
         }