Fix the GN build for MIPS.

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index 509d78afea11a1e700d3fa040092a98c14fa7b68..56fe5179f076a43c794aa5c310a791610f31bdd2 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -33,7 +33,8 @@ v8_toolset_for_d8 = "host"
 # x64 Linux host. Eventually we need to support all of the host/target
 # configurations v8 runs on.
 if (host_cpu == "x64" && host_os == "linux" &&
-    (target_cpu == "arm" || target_cpu == "mipsel" || target_cpu == "x86")) {
+    (target_cpu == "arm" || target_cpu == "mipsel" ||
+     target_cpu == "mips64el" || target_cpu == "x86")) {

[Dirk Pranke, 2015/03/17 21:32:04]

As discussed over chat, I don't think you want this particular change (it would
build the snapshot using 32-bit pointers, and we need to use 64-bit pointers for
mips64el).

[wtc, 2015/03/17 21:42:05]

Done.

   snapshot_toolchain = "//build/toolchain/linux:clang_x86"
 } else {
   snapshot_toolchain = default_toolchain
@@ -113,7 +114,7 @@ config("toolchain") {
   defines = []
   cflags = []
 
-  # TODO(jochen): Add support for arm subarchs, mips, mipsel.
+  # TODO(jochen): Add support for arm subarchs, mips, mipsel, mips64el.

[wtc, 2015/03/17 21:42:05]

Jochen, Michael: does it make sense to add "mips64el" to this TODO comment, or
should I revert this change as well?

 
   if (v8_target_arch == "arm") {
     defines += [ "V8_TARGET_ARCH_ARM" ]
@@ -150,6 +151,12 @@ config("toolchain") {
   if (v8_target_arch == "arm64") {
     defines += [ "V8_TARGET_ARCH_ARM64" ]
   }
+  if (v8_target_arch == "mipsel") {
+    defines += [ "V8_TARGET_ARCH_MIPS" ]
+  }
+  if (v8_target_arch == "mips64el") {
+    defines += [ "V8_TARGET_ARCH_MIPS64" ]
+  }
   if (v8_target_arch == "x86") {
     defines += [ "V8_TARGET_ARCH_IA32" ]
   }