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

test/cctest/cctest.gyp

Index: test/cctest/cctest.gyp
diff --git a/test/cctest/cctest.gyp b/test/cctest/cctest.gyp
index 3f7d56aa431a8f1d998cd568b61d91e3903d6da7..7b39c1ae23a274816d5b901077352abc2df33da6 100644
--- a/test/cctest/cctest.gyp
+++ b/test/cctest/cctest.gyp
@@ -278,17 +278,7 @@
         ['component=="shared_library"', {
           # cctest can't be built against a shared library, so we need to
           # depend on the underlying static target in that case.
-          'conditions': [
-            ['v8_use_snapshot=="true" and v8_use_external_startup_data==0', {
-              'dependencies': ['../../tools/gyp/v8.gyp:v8_snapshot'],
-            }],
-            ['v8_use_snapshot=="true" and v8_use_external_startup_data==1', {
-              'dependencies': ['../../tools/gyp/v8.gyp:v8_external_snapshot'],
-            }],
-            ['v8_use_snapshot!="true"', {
-              'dependencies': ['../../tools/gyp/v8.gyp:v8_nosnapshot'],
-            }],
-          ],
+          'dependencies': ['../../tools/gyp/v8.gyp:v8_maybe_snapshot'],
         }, {
           'dependencies': ['../../tools/gyp/v8.gyp:v8'],
         }],