Move the cros_* GN args to a .gni file and add a bootstrap cros toolchain.

build/toolchain/cros/BUILD.gn

Index: build/toolchain/cros/BUILD.gn
diff --git a/build/toolchain/cros/BUILD.gn b/build/toolchain/cros/BUILD.gn
index 3619828c820346967af168a78f35e2e3f18e0cf7..f2accb2c206d0334c057f55e843648988ce02c7a 100644
--- a/build/toolchain/cros/BUILD.gn
+++ b/build/toolchain/cros/BUILD.gn
@@ -2,80 +2,10 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/config/compiler/compiler.gni")
+import("//build/config/sysroot.gni")
 import("//build/toolchain/gcc_toolchain.gni")
-
-# CrOS builds must cross-compile on a Linux host for the actual CrOS
-# device target. There are many different CrOS devices so the build
-# system provides configuration variables that permit a CrOS build to
-# control the cross-compilation tool chain. However, requiring such
-# fine-grain specification is tedious for build-bots and developers.
-# Consequently, the CrOS build system defaults to a convenience
-# compilation mode where the compilation host is also the build target.
-#
-# Chrome can be compiled in this way with the gn variable:
-#
-# target_os = "chromeos"
-#
-# To perform a board-specific build, first obtain the correct system
-# root (http://goo.gl/aFB4XH) for the board. Then configure GN to use it
-# by setting appropriate cross-compilation variables.
-#
-# For example, to compile a Chrome source tree in /g/src for an
-# auron_paine CrOS device with the system root cached in /g/.cros_cache,
-# the following GN arguments must be provided to configure
-# cross-compilation with Goma acceleration. (NB: additional variables
-# will be necessary to successfully compile a working CrOS Chrome. See
-# the definition of GYP_DEFINES inside a sysroot shell.)
-#
-# goma_dir = "/g/.cros_cache/common/goma+2"
-# target_sysroot= /g/.cros_cache/chrome-sdk/tarballs/auron_paine+7644.0.0+sysroot_chromeos-base_chromeos-chrome.tar.xz"
-# cros_target_cc = "x86_64-cros-linux-gnu-gcc -B/g/.cros_cache/chrome-sdk/tarballs/auron_paine+7657.0.0+target_toolchain/usr/x86_64-pc-linux-gnu/x86_64-cros-linux-gnu/binutils-bin/2.25.51-gold"
-# cros_target_cxx = "x86_64-cros-linux-gnu-g++ -B/g/.cros_cache/chrome-sdk/tarballs/auron_paine+7657.0.0+target_toolchain/usr/x86_64-pc-linux-gnu/x86_64-cros-linux-gnu/binutils-bin/2.25.51-gold"
-# cros_target_ar = "x86_64-cros-linux-gnu-gcc-ar"
-# target_cpu = "x64"
-
-declare_args() {
-  # These must be specified for a board-specific build.
-  cros_target_ar = "ar"
-  cros_target_cc = "gcc"
-  cros_target_cxx = "g++"
-  cros_target_ld = ""
-  cros_target_nm = ""
-  cros_target_readelf = ""
-
-  # These can be optionally set. The "_cppflags"  will be applied to *both*
-  # C and C++ files; use "_cxxflags" for C++-only flags.
-  cros_target_extra_cflags = ""
-  cros_target_extra_cppflags = ""
-  cros_target_extra_cxxflags = ""
-  cros_target_extra_ldflags = ""
-
-  # is_clang is used instead of cros_target_is_clang
-
-  cros_host_ar = "ar"
-  cros_host_cc = "gcc"
-  cros_host_cxx = "g++"
-  cros_host_ld = ""
-  cros_host_nm = ""
-  cros_host_readelf = ""
-  cros_host_extra_cflags = ""
-  cros_host_extra_cppflags = ""
-  cros_host_extra_cxxflags = ""
-  cros_host_extra_ldflags = ""
-  cros_host_is_clang = false
-
-  cros_v8_snapshot_ar = "ar"
-  cros_v8_snapshot_cc = "gcc"
-  cros_v8_snapshot_cxx = "g++"
-  cros_v8_snapshot_ld = ""
-  cros_v8_snapshot_nm = ""
-  cros_v8_snapshot_readelf = ""
-  cros_v8_snapshot_extra_cflags = ""
-  cros_v8_snapshot_extra_cppflags = ""
-  cros_v8_snapshot_extra_cxxflags = ""
-  cros_v8_snapshot_extra_ldflags = ""
-  cros_v8_snapshot_is_clang = false
-}
+import("//build/toolchain/cros_toolchain.gni")
 
 # TODO(dpranke): Delete this after we get rid of the reference to
 # build/toolchain/cros:clang_target in BUILDCONFIG.gn
@@ -84,31 +14,61 @@ clang_toolchain("clang_target") {
   toolchain_os = "linux"
 }
 
-gcc_toolchain("target") {
-  # These are args for the template.
-  ar = cros_target_ar
-  cc = cros_target_cc
-  cxx = cros_target_cxx
-  ld = cxx
-  if (cros_target_ld != "") {
-    ld = cros_target_ld
+template("cros_target_toolchain") {
+  if (defined(invoker.use_debug_fission)) {
+    use_debug_fission = invoker.use_debug_fission
   }
-  if (cros_target_nm != "") {
-    nm = cros_target_nm
+  if (defined(invoker.use_gold)) {
+    use_gold = invoker.use_gold
   }
-  if (cros_target_readelf != "") {
-    readelf = cros_target_readelf
+  if (defined(invoker.use_sysroot)) {
+    use_sysroot = invoker.use_sysroot
   }
-  extra_cflags = cros_target_extra_cflags
-  extra_cppflags = cros_target_extra_cppflags
-  extra_cxxflags = cros_target_extra_cxxflags
-  extra_ldflags = cros_target_extra_ldflags
 
-  # These are passed through as toolchain_args.
-  cc_wrapper = ""
-  is_clang = is_clang
-  toolchain_cpu = target_cpu
-  toolchain_os = "linux"
+  gcc_toolchain(target_name) {
+    # These are args for the template.
+    ar = cros_target_ar
+    cc = cros_target_cc
+    cxx = cros_target_cxx
+    ld = cxx
+    if (cros_target_ld != "") {
+      ld = cros_target_ld
+    }
+    if (cros_target_nm != "") {
+      nm = cros_target_nm
+    }
+    if (cros_target_readelf != "") {
+      readelf = cros_target_readelf
+    }
+    extra_cflags = cros_target_extra_cflags
+    extra_cppflags = cros_target_extra_cppflags
+    extra_cxxflags = cros_target_extra_cxxflags
+    extra_ldflags = cros_target_extra_ldflags
+
+    # These are passed through as toolchain_args.
+    cc_wrapper = ""
+    is_clang = is_clang
+    toolchain_cpu = target_cpu
+    toolchain_os = "chromeos"
+
+    use_debug_fission = use_debug_fission
+    use_gold = use_gold
+    use_sysroot = use_sysroot
+  }
+}
+
+# This is the normal toolchain for most targets.
+cros_target_toolchain("target") {
+}
+
+# This is a special toolchain needed just for the nacl_bootstrap target in
+# //native_client/src/trusted/service_runtime/linux. It is identical
+# to ":target" except that it forces use_debug_fission, use_gold, and
+# use_sysroot off.
+cros_target_toolchain("nacl_bootstrap") {
+  use_debug_fission = false
+  use_gold = false
+  use_sysroot = false
 }
 
 gcc_toolchain("host") {