Land prep work to enable NaCl in the Linux x64 GN builds.

ppapi/native_client/BUILD.gn

+# Copyright 2015 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/features.gni")
+
+if (enable_nacl && enable_nacl_untrusted) {
+  group("ppapi_lib") {
+    deps = [
+      "src/untrusted/irt_stub:ppapi_stub_lib",
+      "//native_client/src/untrusted/pthread",
+    ]
+  }
+
+  executable("nacl_irt") {
+    deps = [
+      "src/untrusted/pnacl_irt_shim:irt",
+      "//base",
+      "//components/tracing",
+      "//gpu/command_buffer/client",
+      "//gpu/command_buffer/common",
+      "//gpu/command_buffer/client:gles2_implementation",
+      "//gpu/ipc",
+      "//ipc",
+      "//media:shared_memory_support",
+      "//native_client/src/untrusted/irt:irt_core_lib",
+      "//native_client/src/shared/srpc",
+      "//native_client/src/shared/platform",
+      "//native_client/src/tools/tls_edit($host_toolchain)",
+      "//native_client/src/untrusted/nacl:imc_syscalls",
+      "//native_client/src/shared/gio",
+      "//ppapi:ppapi_ipc",
+      "//ppapi:ppapi_proxy",
+      "//ppapi:ppapi_shared",
+    ]
+  }
+}