Update Chomium's build files to work w/ latest GN binaries.

build/config/mips.gni

Index: build/config/mips.gni
diff --git a/build/config/mips.gni b/build/config/mips.gni
index f544d9452284276f3f35d6ad789f33af639cb864..512552db1a98e865d700123752020c6d5a63b204 100644
--- a/build/config/mips.gni
+++ b/build/config/mips.gni
@@ -3,11 +3,11 @@
 # found in the LICENSE file.
 
 # MIPS arch variant.
-if (cpu_arch == "mipsel") {
+if (current_cpu == "mipsel") {
   declare_args() {
     mips_arch_variant = "r1"
   }
-} else if (cpu_arch == "mips64el") {
+} else if (current_cpu == "mips64el") {
   if (is_android) {
     declare_args() {
       mips_arch_variant = "r6"