Get GN build working

- Static library
- Add overrides, not necessary yet but it will be when other parts of
  this repo wants to find Vulkan-Headers
- Remove unused dependency on Vulkan-Headers from the settings library
- Remove unreachable return flagged by clang

BUILD.gn

@@ -1,36 +1,20 @@
-# Copyright 2023-2023 The ANGLE Project Authors.
 # Copyright 2023-2023 LunarG, Inc.
 #
 # SPDX-License-Identifier: Apache-2.0
 
-source_set("vulkan_utility_libraries") {
-  include_dirs = [
-    "include",
-  ]
+import("//build_overrides/vulkan_utility_libraries.gni")
+
+static_library("vulkan_layer_settings") {
+  include_dirs = [ "include" ]
   sources = [
+    "include/vulkan/layer/vk_layer_settings.h",
+    "include/vulkan/layer/vk_layer_settings.hpp",
+    "include/vulkan/layer/vk_layer_settings_ext.h",
     "src/layer/layer_settings_manager.cpp",
     "src/layer/layer_settings_manager.hpp",
     "src/layer/layer_settings_util.cpp",
     "src/layer/layer_settings_util.hpp",
     "src/layer/vk_layer_settings.cpp",
     "src/layer/vk_layer_settings_helper.cpp",
-    "include/vulkan/layer/vk_layer_settings_ext.h",
-    "include/vulkan/layer/vk_layer_settings.h",
-    "include/vulkan/layer/vk_layer_settings.hpp",
   ]
-  public_configs = [ ":vulkan_headers_config" ]
-  public_deps = [ "$vulkan_headers_dir:vulkan_headers" ]
 }
-
-if (is_fuchsia) {
-  library_type = "loadable_module"
-} else {
-  library_type = "shared_library"
-}
-
-target(library_type, "vulkan_layer_settings") {
-    defines = []
-    ldflags = []
-    deps = [ ":vulkan_utility_libraries" ]
-}
-

src/layer/vk_layer_settings.cpp

@@ -558,8 +558,6 @@ VkResult vlGetLayerSettingValues(VlLayerSettingSet layerSettingSet, const char *
             return result;
         }
     }
-
-    return VK_ERROR_UNKNOWN;
 }
 
 const VkLayerSettingsCreateInfoEXT *vlFindLayerSettingsCreateInfo(const VkInstanceCreateInfo *pCreateInfo) {