Reland "Turn libbase into a component"

src/base/base-export.h

Index: src/base/base-export.h
diff --git a/src/base/base-export.h b/src/base/base-export.h
new file mode 100644
index 0000000000000000000000000000000000000000..a2b3dacaf73b9144af22a41bf65e5b6ee584863e
--- /dev/null
+++ b/src/base/base-export.h
@@ -0,0 +1,31 @@
+// 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_BASE_BASE_EXPORT_H_
+#define V8_BASE_BASE_EXPORT_H_
+
+#include "include/v8config.h"
+
+#if V8_OS_WIN
+
+#ifdef BUILDING_V8_BASE_SHARED
+#define V8_BASE_EXPORT __declspec(dllexport)
+#elif USING_V8_BASE_SHARED
+#define V8_BASE_EXPORT __declspec(dllimport)
+#else
+#define V8_BASE_EXPORT
+#endif  // BUILDING_V8_BASE_SHARED
+
+#else  // !V8_OS_WIN
+
+// Setup for Linux shared library export.
+#ifdef BUILDING_V8_BASE_SHARED
+#define V8_BASE_EXPORT __attribute__((visibility("default")))
+#else
+#define V8_BASE_EXPORT
+#endif
+
+#endif  // V8_OS_WIN
+
+#endif  // V8_BASE_BASE_EXPORT_H_