Re-land: Enable external startup by default on Linux.

build/standalone.gypi

 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 183 matching lines @@
       }],
       ['tsan==1', {
         'use_custom_libcxx%': 1,
       }],
       ['msan==1', {
         # Use a just-built, MSan-instrumented libc++ instead of the system-wide
         # libstdc++. This is required to avoid false positive reports whenever
         # the C++ standard library is used.
         'use_custom_libcxx%': 1,
       }],
+      ['OS=="linux" and v8_target_arch==host_arch', {
+        # Gradually roll out v8_use_external_startup_data.
+        # Should eventually be default enabled on all platforms.
+        'v8_use_external_startup_data%': 1,
+      }],
     ],
     # Default ARM variable settings.
     'arm_version%': 'default',
     'arm_fpu%': 'vfpv3',
     'arm_float_abi%': 'default',
     'arm_thumb': 'default',
 
     # Default MIPS variable settings.
     'mips_arch_variant%': 'r2',
     # Possible values fp32, fp64, fpxx.
@@ skipping 507 matching lines @@
     ['use_goma==1 and ("<(GENERATOR)"=="ninja" or clang==1)', {
       'make_global_settings': [
        ['CC_wrapper', '<(gomadir)/gomacc'],
        ['CXX_wrapper', '<(gomadir)/gomacc'],
        ['CC.host_wrapper', '<(gomadir)/gomacc'],
        ['CXX.host_wrapper', '<(gomadir)/gomacc'],
       ],
     }],
   ],
 }