Use new toolchain_args variable in GN

build/toolchain/nacl_toolchain.gni

Index: build/toolchain/nacl_toolchain.gni
diff --git a/build/toolchain/nacl_toolchain.gni b/build/toolchain/nacl_toolchain.gni
index ea4c5ec69e77bd2cb61392b6c5a066fe96fce8dc..eb6ffcce0c0bf687483c24ed7192f5c60bd67460 100644
--- a/build/toolchain/nacl_toolchain.gni
+++ b/build/toolchain/nacl_toolchain.gni
@@ -12,25 +12,19 @@ import("//build/toolchain/gcc_toolchain.gni")
 #  - cxx
 #  - ar
 #  - ld
-# and the following which is used in the toolchain_args
-#  - toolchain_cpu  (What "current_cpu" should be set to when invoking a
-#                    build using this toolchain.)
 
 template("nacl_toolchain") {
   assert(defined(invoker.cc), "nacl_toolchain() must specify a \"cc\" value")
   assert(defined(invoker.cxx), "nacl_toolchain() must specify a \"cxx\" value")
   assert(defined(invoker.ar), "nacl_toolchain() must specify a \"ar\" value")
   assert(defined(invoker.ld), "nacl_toolchain() must specify a \"ld\" value")
-  assert(defined(invoker.toolchain_cpu),
-         "nacl_toolchain() must specify a \"toolchain_cpu\"")
   gcc_toolchain(target_name) {
-    toolchain_os = "nacl"
-
     if (defined(invoker.executable_extension)) {
       executable_extension = invoker.executable_extension
     } else {
       executable_extension = ".nexe"
     }
+    rebuild_define = "NACL_TC_REV=" + invoker.toolchain_revision
 
     forward_variables_from(invoker,
                            [
@@ -43,25 +37,19 @@ template("nacl_toolchain") {
                              "nm",
                              "readelf",
                              "strip",
-                             "toolchain_cpu",
                            ])
 
-    if (defined(invoker.is_clang)) {
-      is_clang = invoker.is_clang
-    }
-    if (defined(invoker.is_nacl_glibc)) {
-      is_nacl_glibc = invoker.is_nacl_glibc
-    }
-    if (defined(invoker.symbol_level)) {
-      symbol_level = invoker.symbol_level
-    }
+    toolchain_args = {
+      # Use all values set on the invoker's toolchain_args.
+      forward_variables_from(invoker.toolchain_args, "*")
 
-    # We do not support component builds with the NaCl toolchains.
-    is_component_build = false
+      current_os = "nacl"
 
-    # We do not support tcmalloc in the NaCl toolchains.
-    use_allocator = "none"
+      # We do not support component builds with the NaCl toolchains.
+      is_component_build = false
 
-    rebuild_define = "NACL_TC_REV=" + invoker.toolchain_revision
+      # We do not support tcmalloc in the NaCl toolchains.
+      use_allocator = "none"
+    }
   }
 }