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

build/config/linux/BUILD.gn

 # Copyright (c) 2013 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.
 
 import("//build/config/linux/pkg_config.gni")
 import("//build/config/features.gni")
 import("//build/config/sysroot.gni")
 import("//build/config/ui.gni")
 import("//tools/generate_library_loader/generate_library_loader.gni")
 
@@ skipping 100 matching lines @@
 config("xi") {
   libs = [ "Xi" ]
 }
 
 config("libresolv") {
   libs = [ "resolv" ]
 }
 
 # CrOS doesn't install GTK, gconf or any gnome packages.
 if (!is_chromeos) {
-  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" ]
-  }
-
-  pkg_config("gnome_keyring") {
-    packages = [ "gnome-keyring-1" ]
-  }
-
-  pkg_config("gconf") {
-    packages = [ "gconf-2.0" ]
-    defines = [ "USE_GCONF" ]
+  # These packages should _only_ be expected when building for a target.
+  # If these extra checks are not run, gconf is required when building host
+  # tools for a CrOS build.
+  if (current_toolchain == host_toolchain &&
+      host_toolchain == default_toolchain) {
+    pkg_config("gconf") {
+      packages = [ "gconf-2.0" ]
+      defines = [ "USE_GCONF" ]
+    }
   }
 }
 
 # If brlapi isn't needed, don't require it to be installed.
 if (use_brlapi) {
   config("brlapi_config") {
     defines = [ "USE_BRLAPI" ]
   }
 
   # TODO(GYP) linux_link_brlapi support. Is this needed?
@@ skipping 69 matching lines @@
     "pci_alloc",
     "pci_init",
     "pci_cleanup",
     "pci_scan_bus",
     "pci_fill_info",
     "pci_lookup_name",
   ]
 }
 
 # Looking for libspeechd? Use //third_party/speech-dispatcher