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

test/unittests/unittests.gyp

Index: test/unittests/unittests.gyp
diff --git a/test/unittests/unittests.gyp b/test/unittests/unittests.gyp
index 2ed05b8adc9fb4111b8253de85e8963086e6fc49..eb5d784857c8239b6a258205ddc399eb74e9701b 100644
--- a/test/unittests/unittests.gyp
+++ b/test/unittests/unittests.gyp
@@ -128,17 +128,7 @@
         ['component=="shared_library"', {
           # compiler-unittests 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'],
         }],