Re-work the 'external snapshot' related build rules.

tools/gyp/v8.gyp

 # 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 20 matching lines @@
     'v8_code': 1,
     'v8_random_seed%': 314159265,
     'embed_script%': "",
     'mksnapshot_exec': '<(PRODUCT_DIR)/<(EXECUTABLE_PREFIX)mksnapshot<(EXECUTABLE_SUFFIX)',
   },
   'includes': ['../../build/toolchain.gypi', '../../build/features.gypi'],
   'targets': [
     {
       'target_name': 'v8',
       'dependencies_traverse': 1,
+      'dependencies': ['v8_maybe_snapshot'],
       'conditions': [
         ['want_separate_host_toolset==1', {
           'toolsets': ['host', 'target'],
         }, {
           'toolsets': ['target'],
         }],
-
-        ['v8_use_snapshot=="true" and v8_use_external_startup_data==0', {
-          # The dependency on v8_base should come from a transitive
-          # dependency however the Android toolchain requires libv8_base.a
-          # to appear before libv8_snapshot.a so it's listed explicitly.
-          'dependencies': ['v8_base', 'v8_snapshot'],
-        }],
-        ['v8_use_snapshot!="true" and v8_use_external_startup_data==0', {
-          # The dependency on v8_base should come from a transitive
-          # dependency however the Android toolchain requires libv8_base.a
-          # to appear before libv8_snapshot.a so it's listed explicitly.
-          'dependencies': ['v8_base', 'v8_nosnapshot'],
-        }],
-        ['v8_use_external_startup_data==1 and want_separate_host_toolset==1', {
-          'dependencies': ['v8_base', 'v8_external_snapshot'],
-          'target_conditions': [
-            ['_toolset=="host"', {
-              'inputs': [
-                '<(PRODUCT_DIR)/snapshot_blob_host.bin',
-              ],
-            }, {
-              'inputs': [
-                '<(PRODUCT_DIR)/snapshot_blob.bin',
-              ],
-            }],
-          ],
-        }],
-        ['v8_use_external_startup_data==1 and want_separate_host_toolset==0', {
-          'dependencies': ['v8_base', 'v8_external_snapshot'],
-          'inputs': [ '<(PRODUCT_DIR)/snapshot_blob.bin', ],
-        }],
         ['component=="shared_library"', {
           'type': '<(component)',
           'sources': [
             # Note: on non-Windows we still build this file so that gyp
             # has some sources to link into the component.
             '../../src/v8dll-main.cc',
           ],
           'include_dirs': [
             '../..',
           ],
@@ skipping 32 matching lines @@
           'type': 'none',
         }],
       ],
       'direct_dependent_settings': {
         'include_dirs': [
           '../../include',
         ],
       },
     },
     {
+      # This rule delegates to either v8_snapshot, v8_nosnapshot, or
+      # v8_external_snapshot, depending on the current variables.
+      # The intention is to make the 'calling' rules a bit simpler.
+      'target_name': 'v8_maybe_snapshot',
+      'type': 'none',
+      'conditions': [
+        ['v8_use_snapshot!="true"', {
+          # The dependency on v8_base should come from a transitive
+          # dependency however the Android toolchain requires libv8_base.a
+          # to appear before libv8_snapshot.a so it's listed explicitly.
+          'dependencies': ['v8_base', 'v8_nosnapshot'],
+        }],
+        ['v8_use_snapshot=="true" and v8_use_external_startup_data==0', {
+          # The dependency on v8_base should come from a transitive
+          # dependency however the Android toolchain requires libv8_base.a
+          # to appear before libv8_snapshot.a so it's listed explicitly.
+          'dependencies': ['v8_base', 'v8_snapshot'],
+        }],
+        ['v8_use_snapshot=="true" and v8_use_external_startup_data==1 and want_separate_host_toolset==0', {
+          'dependencies': ['v8_base', 'v8_external_snapshot'],
+          'inputs': [ '<(PRODUCT_DIR)/snapshot_blob.bin', ],
+        }],
+        ['v8_use_snapshot=="true" and v8_use_external_startup_data==1 and want_separate_host_toolset==1', {
+          'dependencies': ['v8_base', 'v8_external_snapshot'],
+          'target_conditions': [
+            ['_toolset=="host"', {
+              'inputs': [
+                '<(PRODUCT_DIR)/snapshot_blob_host.bin',
+              ],
+            }, {
+              'inputs': [
+                '<(PRODUCT_DIR)/snapshot_blob.bin',
+              ],
+            }],
+          ],
+        }],
+        ['want_separate_host_toolset==1', {
+          'toolsets': ['host', 'target'],
+        }, {
+          'toolsets': ['target'],
+        }],
+      ]
+    },
+    {
       'target_name': 'v8_snapshot',
       'type': 'static_library',
       'conditions': [
         ['want_separate_host_toolset==1', {
           'toolsets': ['host', 'target'],
           'dependencies': [
             'mksnapshot#host',
             'js2c#host',
           ],
         }, {
@@ skipping 1688 matching lines @@
         }],
         ['want_separate_host_toolset==1', {
           'toolsets': ['host'],
         }, {
           'toolsets': ['target'],
         }],
       ],
     },
   ],
 }