GN: Respect system libdir whenever building with the traget sysroot

build/config/linux/pkg_config.gni

 # 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/sysroot.gni")
 
 # Defines a config specifying the result of running pkg-config for the given
 # packages. Put the package names you want to query in the "packages" variable
 # inside the template invocation.
 #
@@ skipping 47 matching lines @@
   ]
 } else if (pkg_config != "") {
   pkg_config_args = [
     "-p",
     pkg_config,
   ]
 } else {
   pkg_config_args = []
 }
 
-# Only use the custom libdir when building with the default toolchain.
-if (current_toolchain == default_toolchain) {
+# Only use the custom libdir when building with the target sysroot.
+if (target_sysroot != "" && sysroot == target_sysroot) {
   pkg_config_args += [
     "--system_libdir",
     system_libdir,
   ]
 }
 
 template("pkg_config") {
   assert(defined(invoker.packages),
          "Variable |packages| must be defined to be a list in pkg_config.")
   config(target_name) {
@@ skipping 12 matching lines @@
       ldflags = pkgresult[4]
     }
 
     forward_variables_from(invoker,
                            [
                              "defines",
                              "visibility",
                            ])
   }
 }