Turn libplatform into a component

src/v8.gyp

Index: src/v8.gyp
diff --git a/src/v8.gyp b/src/v8.gyp
index 94b9d513f63028a0aff48b416a47305ab829e831..b104b08c1283d10e989f099969433eaa10f221c7 100644
--- a/src/v8.gyp
+++ b/src/v8.gyp
@@ -2056,7 +2056,7 @@
     },
     {
       'target_name': 'v8_libplatform',
-      'type': 'static_library',
+      'type': '<(component)',
       'variables': {
         'optimize': 'max',
       },
@@ -2070,6 +2070,7 @@
       ],
       'sources': [
         '../include/libplatform/libplatform.h',
+        '../include/libplatform/libplatform-export.h',
         '../include/libplatform/v8-tracing.h',
         'libplatform/default-platform.cc',
         'libplatform/default-platform.h',
@@ -2091,6 +2092,12 @@
         }, {
           'toolsets': ['target'],
         }],
+        ['component=="shared_library"', {
+          'direct_dependent_settings': {
+            'defines': [ 'USING_V8_PLATFORM_SHARED' ],
+          },
+          'defines': [ 'BUILDING_V8_PLATFORM_SHARED' ],
+        }]
       ],
       'direct_dependent_settings': {
         'include_dirs': [