add nacl_toolchain to //build and flip to using it in the GN build.

build/config/nacl/nacl_defines.gni

Index: build/config/nacl/nacl_defines.gni
diff --git a/build/config/nacl/nacl_defines.gni b/build/config/nacl/nacl_defines.gni
new file mode 100644
index 0000000000000000000000000000000000000000..2297a07a5e47b29b67a8cd416c81a8f7d4a9f027
--- /dev/null
+++ b/build/config/nacl/nacl_defines.gni
@@ -0,0 +1,61 @@
+# Copyright (c) 2014 The Chromium Authors. All rights reserved.

[Dirk Pranke, 2015/08/28 02:29:41]

This file is simply copied over from
//native_client/build/config/nacl/nacl_defines.gni .

A comment from mseaborn yesterday indicated that much of this is no longer
needed, but I would prefer to clean that up in a subsequent patch.

[brettw, 2015/08/28 19:08:38]

Just noticed this... it seems just as easy to copy-and-paste this into the
nacl_defines target. I'm not sure why this would be easier to clean up in a
separate step.

+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+nacl_defines = [

[brettw, 2015/08/28 18:25:52]

I don't see why this is in a .gni file and not just applied inline in the
nacl_defines config. Unless you can see an obvious use, we should just move this
there.

[Dirk Pranke, 2015/08/28 20:08:32]

Acknowledged.

+  "NACL_ANDROID=0",
+  "_DEFAULT_SOURCE=1",
+  "_BSD_SOURCE=1",
+  "_POSIX_C_SOURCE=199506",
+  "_XOPEN_SOURCE=600",
+  "_GNU_SOURCE=1",
+  "_LARGEFILE64_SOURCE=1",

[brettw, 2015/08/28 18:25:52]

Looks like this is already defined in build/config/compiler:compiler for all
posix builds. I think you can remove this line.

[Dirk Pranke, 2015/08/28 20:08:31]

Acknowledged.

+  "__STDC_LIMIT_MACROS=1",
+  "__STDC_FORMAT_MACROS=1",

[brettw, 2015/08/28 18:25:52]

__STDC_FORMAT_MACROS is set automatically by chromium_code. I think the relevant
nacl targets should be compiled with this config, so you can remove it.

[Dirk Pranke, 2015/08/28 20:08:32]

Acknowledged.

+]
+
+if (is_win) {
+  nacl_defines += [ "NACL_WINDOWS=1" ]
+} else {
+  nacl_defines += [ "NACL_WINDOWS=0" ]
+}
+
+if (is_linux) {
+  nacl_defines += [ "NACL_LINUX=1" ]
+} else {
+  nacl_defines += [ "NACL_LINUX=0" ]
+}
+
+if (is_mac) {
+  nacl_defines += [ "NACL_OSX=1" ]
+} else {
+  nacl_defines += [ "NACL_OSX=0" ]
+}
+
+if (current_cpu == "arm") {
+  nacl_defines += [
+    "NACL_BUILD_ARCH=arm",
+    "NACL_BUILD_SUBARCH=32",
+  ]
+}
+
+if (current_cpu == "mips") {
+  nacl_defines += [
+    "NACL_BUILD_ARCH=mips",
+    "NACL_BUILD_SUBARCH=32",
+  ]
+}
+
+if (current_cpu == "x86") {
+  nacl_defines += [
+    "NACL_BUILD_ARCH=x86",
+    "NACL_BUILD_SUBARCH=32",
+  ]
+}
+
+if (current_cpu == "x64") {
+  nacl_defines += [
+    "NACL_BUILD_ARCH=x86",
+    "NACL_BUILD_SUBARCH=64",
+  ]
+}