gn build changes for v8

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index eaf56dd9db26b4e3733ea3da4c864bfe1d5e1ff3..e5f6ed94f1e0520b47caaaec777f8877ce7a9528 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -19,6 +19,9 @@ v8_object_print = false
 v8_postmortem_support = false
 v8_use_snapshot = true
 v8_target_arch = current_cpu
+if (enable_correct_v8_arch) {
+  v8_target_arch = target_cpu
+}
 v8_random_seed = "314159265"
 v8_toolset_for_d8 = "host"
 
@@ -56,6 +59,15 @@ config("external_config") {
   include_dirs = [ "include" ]
 }
 
+declare_args() {
+  host_cxx_is_biarch = 0
+  if (enable_correct_v8_arch &&
+      (host_cpu == "ia32" || host_cpu =="x64" || host_cpu=="ppc" ||
+       host_cpu=="ppc64" || is_clang)) {
+    host_cxx_is_biarch = 1
+  }
+}
+
 config("features") {
   visibility = [ ":*" ]  # Only targets in this file can depend on this.
 
@@ -95,6 +107,7 @@ config("toolchain") {
 
   defines = []
   cflags = []
+  ldflags = []
 
   # TODO(jochen): Add support for arm subarchs, mips, mipsel.
 
@@ -151,6 +164,21 @@ config("toolchain") {
       "OPTIMIZED_DEBUG",
     ]
   }
+
+  if ((current_os == "linux" || current_os == "freebsd" ||
+       current_os == "openbsd" || current_os == "solaris" ||
+       current_os == "netbsd" || current_os == "mac" ||
+       current_os == "android" || current_os == "qnx") &&
+      (v8_target_arch == "arm" || v8_target_arch == "ia32" ||
+       v8_target_arch == "x87" || v8_target_arch == "mips" ||
+       v8_target_arch == "mipsel" || v8_target_arch == "ppc")) {
+    if (current_toolchain == host_toolchain) {
+      if (host_cxx_is_biarch == 1) {
+        cflags += [ "-m32" ]
+        ldflags += [ "-m32" ]
+      }
+    }
+  }
 }
 
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