Use new toolchain_args variable in GN

build/toolchain/cros/BUILD.gn

 # Copyright 2014 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/compiler/compiler.gni")
 import("//build/config/sysroot.gni")
 import("//build/toolchain/gcc_toolchain.gni")
 import("//build/toolchain/cros_toolchain.gni")
 
 template("cros_target_toolchain") {
-  if (defined(invoker.use_debug_fission)) {
-    use_debug_fission = invoker.use_debug_fission
-  }
-  if (defined(invoker.use_gold)) {
-    use_gold = invoker.use_gold
-  }
-  if (defined(invoker.use_sysroot)) {
-    use_sysroot = invoker.use_sysroot
-  }
+  gcc_toolchain(target_name) {
+    assert(defined(invoker.toolchain_args))
 
-  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"
+    toolchain_args = {
+      forward_variables_from(invoker.toolchain_args, "*")
 
-    use_debug_fission = use_debug_fission
-    use_gold = use_gold
-    use_sysroot = use_sysroot
+      cc_wrapper = ""
+
+      # This will override the default computation for is_clang in the
+      # secondary toolchain with the value of is_clang in the current toolchain
+      # (the current toolchain will always be the default toolchain here).
+      is_clang = is_clang
+      current_cpu = target_cpu
+      current_os = "chromeos"
+      use_debug_fission = use_debug_fission
+      use_sysroot = use_sysroot
+    }
   }
 }
 
 # This is the normal toolchain for most targets.
 cros_target_toolchain("target") {
+  toolchain_args = {
+  }
 }
 
 # 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
+  toolchain_args = {
+    use_debug_fission = false
+    use_gold = false
+    use_sysroot = false
+  }
 }
 
 gcc_toolchain("host") {
   # These are args for the template.
   ar = cros_host_ar
   cc = cros_host_cc
   cxx = cros_host_cxx
   ld = cxx
   if (cros_host_ld != "") {
     ld = cros_host_ld
   }
   if (cros_host_nm != "") {
     nm = cros_host_nm
   }
   if (cros_host_readelf != "") {
     readelf = cros_host_readelf
   }
   extra_cflags = cros_host_extra_cflags
   extra_cppflags = cros_host_extra_cppflags
   extra_cxxflags = cros_host_extra_cxxflags
   extra_ldflags = cros_host_extra_ldflags
 
-  # These are passed through as toolchain_args.
-  cc_wrapper = ""
-  is_clang = cros_host_is_clang
-  toolchain_cpu = host_cpu
-  toolchain_os = "linux"
-  use_sysroot = false
+  toolchain_args = {
+    cc_wrapper = ""
+    is_clang = cros_host_is_clang
+    current_cpu = host_cpu
+    current_os = "linux"
+    use_sysroot = false
+  }
 }
 
 gcc_toolchain("v8_snapshot") {
   # These are args for the template.
   ar = cros_v8_snapshot_ar
   cc = cros_v8_snapshot_cc
   cxx = cros_v8_snapshot_cxx
   ld = cxx
   if (cros_v8_snapshot_ld != "") {
     ld = cros_v8_snapshot_ld
   }
   if (cros_v8_snapshot_nm != "") {
     nm = cros_v8_snapshot_nm
   }
   if (cros_v8_snapshot_readelf != "") {
     readelf = cros_v8_snapshot_readelf
   }
   extra_cflags = cros_v8_snapshot_extra_cflags
   extra_cppflags = cros_v8_snapshot_extra_cppflags
   extra_cxxflags = cros_v8_snapshot_extra_cxxflags
   extra_ldflags = cros_v8_snapshot_extra_ldflags
 
-  # These are passed through as toolchain_args.
-  cc_wrapper = ""
-  is_clang = cros_v8_snapshot_is_clang
-  if (target_cpu == "x86" || target_cpu == "arm" || target_cpu == "mipsel") {
-    toolchain_cpu = "x86"
-  } else {
-    toolchain_cpu = "x64"
+  toolchain_args = {
+    cc_wrapper = ""
+    is_clang = cros_v8_snapshot_is_clang
+    if (target_cpu == "x86" || target_cpu == "arm" || target_cpu == "mipsel") {
+      current_cpu = "x86"
+    } else {
+      current_cpu = "x64"
+    }
+    v8_toolchain_cpu = v8_target_cpu
+    current_os = "linux"
+    use_sysroot = false
   }
-  v8_toolchain_cpu = v8_target_cpu
-  toolchain_os = "linux"
-  use_sysroot = false
 }