Add support for building v8 on mips and mips64 using GN.

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 5b7689f9f2d31f796a990252e16430fb3d08ad12..f09901941d4006625756ff0c72bf010267799071 100644
--- a/build/toolchain/linux/BUILD.gn
+++ b/build/toolchain/linux/BUILD.gn
@@ -83,6 +83,14 @@ clang_toolchain("clang_x86_v8_mipsel") {
   }
 }
 
+clang_toolchain("clang_x86_v8_mips") {
+  toolchain_args = {
+    current_cpu = "x86"
+    v8_current_cpu = "mips"
+    current_os = "linux"
+  }
+}
+
 gcc_toolchain("x86") {
   cc = "gcc"
   cxx = "g++"
@@ -128,6 +136,14 @@ clang_toolchain("clang_x64_v8_mips64el") {
   }
 }
 
+clang_toolchain("clang_x64_v8_mips64") {
+  toolchain_args = {
+    current_cpu = "x64"
+    v8_current_cpu = "mips64"
+    current_os = "linux"
+  }
+}
+
 gcc_toolchain("x64") {
   cc = "gcc"
   cxx = "g++"
@@ -202,3 +218,35 @@ gcc_toolchain("ppc64") {
     is_clang = false
   }
 }
+
+gcc_toolchain("mips") {
+  cc = "gcc"
+  cxx = "g++"
+
+  readelf = "readelf"
+  nm = "nm"
+  ar = "ar"
+  ld = cxx
+
+  toolchain_args = {
+    current_cpu = "mips"
+    current_os = "linux"
+    is_clang = false
+  }
+}
+
+gcc_toolchain("mips64") {
+  cc = "gcc"
+  cxx = "g++"
+
+  readelf = "readelf"
+  nm = "nm"
+  ar = "ar"
+  ld = cxx
+
+  toolchain_args = {
+    current_cpu = "mips64"
+    current_os = "linux"
+    is_clang = false
+  }
+}