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

build/config/mips.gni

Index: build/config/mips.gni
diff --git a/build/config/mips.gni b/build/config/mips.gni
index 5604ca66f2548f229ba714c0f8fb15f290d32800..ca582e10853e82d14b5c78ca13c1f19dfa83e617 100644
--- a/build/config/mips.gni
+++ b/build/config/mips.gni
@@ -8,7 +8,8 @@ import("//build/config/v8_target_cpu.gni")
 # MIPS code is being compiled.  But they can also be relevant in the
 # other contexts when the code will change its behavior based on the
 # cpu it wants to generate code for.
-if (current_cpu == "mipsel" || v8_current_cpu == "mipsel") {
+if (current_cpu == "mipsel" || v8_current_cpu == "mipsel" ||
+    current_cpu == "mips" || v8_current_cpu == "mips") {
   declare_args() {
     # MIPS arch variant. Possible values are:
     #   "r1"
@@ -36,7 +37,8 @@ if (current_cpu == "mipsel" || v8_current_cpu == "mipsel") {
     #   "fpxx": sets the GCC -mfpxx option.
     mips_fpu_mode = "fp32"
   }
-} else if (current_cpu == "mips64el" || v8_current_cpu == "mips64el") {
+} else if (current_cpu == "mips64el" || v8_current_cpu == "mips64el" ||
+           current_cpu == "mips64" || v8_current_cpu == "mips64") {
   # MIPS arch variant. Possible values are:
   #   "r2"
   #   "r6"