GN: Refactor Linux Clang toolchain definitions, plumb use_gold for toolchain_args()

build/toolchain/linux/BUILD.gn

 # Copyright 2013 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/sysroot.gni")
 import("//build/toolchain/gcc_toolchain.gni")
 
-gcc_toolchain("clang_arm") {
-  prefix = rebase_path("//third_party/llvm-build/Release+Asserts/bin",
-                       root_build_dir)
-  cc = "$prefix/clang"
-  cxx = "$prefix/clang++"
-
-  toolprefix = "arm-linux-gnueabihf-"
-  readelf = "${toolprefix}readelf"
-  ar = "${toolprefix}ar"
-  ld = cxx
-  readelf = "${toolprefix}readelf"
-  nm = "${toolprefix}nm"
-
+clang_toolchain("clang_arm") {
   toolchain_cpu = "arm"
   toolchain_os = "linux"
-  is_clang = true
+  toolprefix = "arm-linux-gnueabihf-"
 }
 
 gcc_toolchain("arm") {
   toolprefix = "arm-linux-gnueabihf-"
 
   cc = "${toolprefix}gcc"
   cxx = "${toolprefix}g++"
 
   ar = "${toolprefix}ar"
   ld = cxx
   readelf = "${toolprefix}readelf"
   nm = "${toolprefix}nm"
 
   toolchain_cpu = "arm"
   toolchain_os = "linux"
   is_clang = false
 }
 
-gcc_toolchain("clang_x86") {
-  prefix = rebase_path("//third_party/llvm-build/Release+Asserts/bin",
-                       root_build_dir)
-  cc = "$prefix/clang"
-  cxx = "$prefix/clang++"
-  readelf = "readelf"
-  nm = "nm"
-  ar = "ar"
-  ld = cxx
-
+clang_toolchain("clang_x86") {
   toolchain_cpu = "x86"
   toolchain_os = "linux"
-  is_clang = true
 }
 
 gcc_toolchain("x86") {
   cc = "gcc"
   cxx = "g++"
 
   readelf = "readelf"
   nm = "nm"
   ar = "ar"
   ld = cxx
 
   toolchain_cpu = "x86"
   toolchain_os = "linux"
   is_clang = false
 }
 
-gcc_toolchain("clang_x64") {
-  prefix = rebase_path("//third_party/llvm-build/Release+Asserts/bin",
-                       root_build_dir)
-  cc = "$prefix/clang"
-  cxx = "$prefix/clang++"
-
-  readelf = "readelf"
-  nm = "nm"
-  ar = "ar"
-  ld = cxx
-
+clang_toolchain("clang_x64") {
   toolchain_cpu = "x64"
   toolchain_os = "linux"
-  is_clang = true
 }
 
 gcc_toolchain("x64") {
   cc = "gcc"
   cxx = "g++"
 
   readelf = "readelf"
   nm = "nm"
   ar = "ar"
   ld = cxx
@@ skipping 10 matching lines @@
   ld = cxx
   readelf = "mipsel-linux-gnu-readelf"
   nm = "mipsel-linux-gnu-nm"
 
   toolchain_cpu = "mipsel"
   toolchain_os = "linux"
   is_clang = false
   use_ccache = false
   use_goma = false
 }