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

build/toolchain/linux/BUILD.gn

Index: build/toolchain/linux/BUILD.gn
diff --git a/build/toolchain/linux/BUILD.gn b/build/toolchain/linux/BUILD.gn
index d74457386ab5e7a11a2de60eaf13e048c7cb604e..f62b99a7c696c9af588b0f5781fd0c08d8fabd9c 100644
--- a/build/toolchain/linux/BUILD.gn
+++ b/build/toolchain/linux/BUILD.gn
@@ -71,3 +71,15 @@ gcc_toolchain("x64") {
   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"
+}