GN: Move configs for single-use Linux packages close to usage

chrome/browser/ui/libgtk2ui/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 assert(is_linux, "This file should only be referenced on Linux")
 
 import("//build/config/features.gni")
+import("//build/config/linux/pkg_config.gni")
+
+pkg_config("gtk") {
+  # Gtk requires gmodule, but it does not list it as a dependency in some
+  # misconfigured systems.
+  packages = [ "gmodule-2.0", "gtk+-2.0", "gthread-2.0" ]
+}
+
+pkg_config("gtkprint") {
+  packages = [ "gtk+-unix-print-2.0" ]
+}
 
 component("libgtk2ui") {
   sources = [
     "app_indicator_icon.cc",
     "app_indicator_icon.h",
     "app_indicator_icon_menu.cc",
     "app_indicator_icon_menu.h",
     "chrome_gtk_frame.cc",
     "chrome_gtk_frame.h",
     "chrome_gtk_menu_subclasses.cc",
@@ skipping 45 matching lines @@
   }
   if (is_clang) {
     # G_DEFINE_TYPE automatically generates a *get_instance_private inline
     # function after glib 2.37. That's unused. Prevent to complain about it.
     cflags = [ "-Wno-unused-function" ]
   }
 
   defines = [ "LIBGTK2UI_IMPLEMENTATION" ]
 
   configs += [
+    ":gtk",
+    ":gtkprint",
     "//build/config/linux:gconf",
-    "//build/config/linux:gtk",
-    "//build/config/linux:gtkprint",
     "//printing:cups",
   ]
 
   deps = [
     "//base",
     "//base:i18n",
     "//base/third_party/dynamic_annotations",
     "//chrome/app/theme:theme_resources",
     "//chrome:extra_resources",
     "//chrome:resources",
     "//chrome:strings",
     "//components/resources",
     "//skia",
     "//ui/base",
     "//ui/resources",
     "//ui/strings",
     "//ui/views",
   ]
 }