Update GN build to use v8_target_cpu instead of v8_target_arch.

test/unittests/BUILD.gn

 # Copyright 2016 The V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Please keep this file in sync with unittests.gyp.
 
 import("../../gni/v8.gni")
 
 v8_executable("unittests") {
   testonly = true
@@ skipping 100 matching lines @@
     "wasm/control-transfer-unittest.cc",
     "wasm/decoder-unittest.cc",
     "wasm/encoder-unittest.cc",
     "wasm/leb-helper-unittest.cc",
     "wasm/loop-assignment-analysis-unittest.cc",
     "wasm/module-decoder-unittest.cc",
     "wasm/switch-logic-unittest.cc",
     "wasm/wasm-macro-gen-unittest.cc",
   ]
 
-  if (v8_target_arch == "arm") {
+  if (v8_target_cpu == "arm") {
     sources += [ "compiler/arm/instruction-selector-arm-unittest.cc" ]
-  } else if (v8_target_arch == "arm64") {
+  } else if (v8_target_cpu == "arm64") {
     sources += [ "compiler/arm64/instruction-selector-arm64-unittest.cc" ]
-  } else if (v8_target_arch == "x86") {
+  } else if (v8_target_cpu == "x86") {
     sources += [ "compiler/ia32/instruction-selector-ia32-unittest.cc" ]
-  } else if (v8_target_arch == "mips" || v8_target_arch == "mipsel") {
+  } else if (v8_target_cpu == "mips" || v8_target_cpu == "mipsel") {
     sources += [ "compiler/mips/instruction-selector-mips-unittest.cc" ]
-  } else if (v8_target_arch == "mips64" || v8_target_arch == "mips64el") {
+  } else if (v8_target_cpu == "mips64" || v8_target_cpu == "mips64el") {
     sources += [ "compiler/mips64/instruction-selector-mips64-unittest.cc" ]
-  } else if (v8_target_arch == "x64") {
+  } else if (v8_target_cpu == "x64") {
     sources += [ "compiler/x64/instruction-selector-x64-unittest.cc" ]
-  } else if (v8_target_arch == "ppc" || v8_target_arch == "ppc64") {
+  } else if (v8_target_cpu == "ppc" || v8_target_cpu == "ppc64") {
     sources += [ "compiler/ppc/instruction-selector-ppc-unittest.cc" ]
-  } else if (v8_target_arch == "s390" || v8_target_arch == "s390x") {
+  } else if (v8_target_cpu == "s390" || v8_target_cpu == "s390x") {
     sources += [ "compiler/s390/instruction-selector-s390-unittest.cc" ]
   }
 
   configs = [
     "../..:external_config",
     "../..:internal_config_base",
   ]
 
   # TODO(machenbach): Translate from gyp.
   #['OS=="aix"', {
@@ skipping 24 matching lines @@
 
     # Suppress warnings about importing locally defined symbols.
     if (is_component_build) {
       ldflags = [
         "/ignore:4049",
         "/ignore:4217",
       ]
     }
   }
 }