[MIPS] Define gcc_toolchain in BUILD.gn for Chromium-Linux

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("../clang.gni")
 import("../goma.gni")
 import("../gcc_toolchain.gni")
 
 if (is_gyp) {
   # Set the compilers for GYP to use. This logic is only relevant to GYP where
@@ skipping 53 matching lines @@
 
 gcc_toolchain("x64") {
   cc = "gcc"
   cxx = "g++"
   ar = "ar"
   ld = cxx
 
   toolchain_cpu_arch = "x64"
   toolchain_os = "linux"
 }
+
+# MIPS -----------------------------------------------------------------------
+
+gcc_toolchain("mipsel") {
+  cc = "mipsel-linux-gnu-gcc"
+  cxx = "mipsel-linux-gnu-g++"
+  ar = "mipsel-linux-gnu-ar"
+  ld = cxx
+
+  toolchain_cpu_arch = "mipsel"
+  toolchain_os = "linux"
+}