Remove support for MSVC

sky/engine/platform/PlatformExport.h

Index: sky/engine/platform/PlatformExport.h
diff --git a/sky/engine/platform/PlatformExport.h b/sky/engine/platform/PlatformExport.h
index 8230fbb80fe30d491e97ecfdbeea00502c290466..e8f6e572e19b6aa82e77fc16abdd7f7da698b60f 100644
--- a/sky/engine/platform/PlatformExport.h
+++ b/sky/engine/platform/PlatformExport.h
@@ -37,30 +37,9 @@
 #endif
 
 #if defined(COMPONENT_BUILD)
-#if defined(WIN32)
-#if BLINK_PLATFORM_IMPLEMENTATION
-#define PLATFORM_EXPORT __declspec(dllexport)
-#else
-#define PLATFORM_EXPORT __declspec(dllimport)
-#endif
-#else // defined(WIN32)
 #define PLATFORM_EXPORT __attribute__((visibility("default")))
-#endif
 #else // defined(COMPONENT_BUILD)
 #define PLATFORM_EXPORT
 #endif
 
-#if defined(_MSC_VER)
-// MSVC Compiler warning C4275:
-// non dll-interface class 'Bar' used as base for dll-interface class 'Foo'.
-// Note that this is intended to be used only when no access to the base class'
-// static data is done through derived classes or inline methods. For more info,
-// see http://msdn.microsoft.com/en-us/library/3tdb471s(VS.80).aspx
-//
-// This pragma will allow exporting a class that inherits from a non-exported
-// base class, anywhere in the Blink platform component. This is only
-// a problem when using the MSVC compiler on Windows.
-#pragma warning(suppress:4275)
-#endif
-
 #endif // PlatformExport_h