MIPS[64]: Add support for big endian build using GN

Chromium_BUG=616017
R=machenbach@chromium.org, dpranke@chromium.org, ivica.bogosavljevic@imgtec.com

Review-Url: https://codereview.chromium.org/2913353004
Cr-Commit-Position: refs/heads/master@{#45691}

BUILD.gn

@@ -337,8 +337,7 @@ config("toolchain") {
     defines += [ "_MIPS_TARGET_SIMULATOR" ]
   }
 
-  # TODO(jochen): Add support for mips.
-  if (v8_current_cpu == "mipsel") {
+  if (v8_current_cpu == "mipsel" || v8_current_cpu == "mips") {
     defines += [ "V8_TARGET_ARCH_MIPS" ]
     if (v8_can_use_fpu_instructions) {
       defines += [ "CAN_USE_FPU_INSTRUCTIONS" ]
@@ -372,15 +371,17 @@ config("toolchain") {
     # TODO(jochen): Add support for mips_arch_variant rx and loongson.
   }
 
-  # TODO(jochen): Add support for mips64.
-  if (v8_current_cpu == "mips64el") {
+  if (v8_current_cpu == "mips64el" || v8_current_cpu == "mips64") {
     defines += [ "V8_TARGET_ARCH_MIPS64" ]
     if (v8_can_use_fpu_instructions) {
       defines += [ "CAN_USE_FPU_INSTRUCTIONS" ]
     }
 
-    # TODO(jochen): Add support for big endian host byteorder.
+    if (host_byteorder == "little") {
       defines += [ "V8_TARGET_ARCH_MIPS64_LE" ]
+    } else if (host_byteorder == "big") {
+      defines += [ "V8_TARGET_ARCH_MIPS64_BE" ]
+    }
     if (v8_use_mips_abi_hardfloat) {
       defines += [
         "__mips_hard_float=1",

snapshot_toolchain.gni

@@ -76,9 +76,11 @@ if (v8_snapshot_toolchain == "") {
 
     if (v8_current_cpu == "x64" || v8_current_cpu == "x86") {
       _cpus = v8_current_cpu
-    } else if (v8_current_cpu == "arm64" || v8_current_cpu == "mips64el") {
+    } else if (v8_current_cpu == "arm64" || v8_current_cpu == "mips64el" ||
+               v8_current_cpu == "mips64") {
       _cpus = "x64_v8_${v8_current_cpu}"
-    } else if (v8_current_cpu == "arm" || v8_current_cpu == "mipsel") {
+    } else if (v8_current_cpu == "arm" || v8_current_cpu == "mipsel" ||
+               v8_current_cpu == "mips") {
       _cpus = "x86_v8_${v8_current_cpu}"
     } else {
       # This branch should not be reached; leave _cpus blank so the assert