move v8_use_external_startup_data to standalone.gypi

build/standalone.gypi

Index: build/standalone.gypi
diff --git a/build/standalone.gypi b/build/standalone.gypi
index 76fa7191eb54954e48ccd7439236cf0b94257d6c..a95c99712a2c6621ba0a1bcbd7dd8626b3331ab8 100644
--- a/build/standalone.gypi
+++ b/build/standalone.gypi
@@ -93,6 +93,10 @@
     #     near-release speeds.
     'v8_optimized_debug%': 0,
 
+    # Use external files for startup data blobs:
+    # the JS builtins sources and the start snapshot.
+    'v8_use_external_startup_data%': 0,
+
     # Relative path to icu.gyp from this file.
     'icu_gyp_path': '../third_party/icu/icu.gyp',
 
@@ -449,5 +453,10 @@
         ['CC', '<(make_clang_dir)/bin/clang-cl'],
       ],
     }],
+    ['v8_use_external_startup_data==1', {
+      'target_defaults': {
+        'defines': ['V8_USE_EXTERNAL_STARTUP_DATA',],
+      },
+    }],
   ],
 }