Treat V8 platform symbols same as base

This exports V8 platform symbols in the Node shared library build.

Author: sparist

tools/v8_gypfiles/v8.gyp

@@ -1457,10 +1457,7 @@
         '<(V8_ROOT)/src/libplatform/worker-thread.h',
       ],
       'conditions': [
-        ['component=="shared_library"', {
-          'direct_dependent_settings': {
-            'defines': ['USING_V8_PLATFORM_SHARED'],
-          },
+        ['is_component_build', {
           'defines': ['BUILDING_V8_PLATFORM_SHARED'],
         }],
         ['v8_use_perfetto==1', {