Turn libplatform into a component

include/libplatform/libplatform-export.h

+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef V8_LIBPLATFORM_LIBPLATFORM_EXPORT_H_
+#define V8_LIBPLATFORM_LIBPLATFORM_EXPORT_H_
+
+#if defined(_WIN32)
+
+#ifdef BUILDING_V8_PLATFORM_SHARED
+#define V8_PLATFORM_EXPORT __declspec(dllexport)
+#elif USING_V8_PLATFORM_SHARED
+#define V8_PLATFORM_EXPORT __declspec(dllimport)
+#else
+#define V8_PLATFORM_EXPORT
+#endif  // BUILDING_V8_PLATFORM_SHARED
+
+#else  // defined(_WIN32)
+
+// Setup for Linux shared library export.
+#if V8_HAS_ATTRIBUTE_VISIBILITY
+#ifdef BUILDING_V8_PLATFORM_SHARED
+#define V8_PLATFORM_EXPORT __attribute__((visibility("default")))
+#else
+#define V8_PLATFORM_EXPORT
+#endif
+#else
+#define V8_PLATFORM_EXPORT
+#endif
+
+#endif  // defined(_WIN32)
+
+#endif  // V8_LIBPLATFORM_LIBPLATFORM_EXPORT_H_