Reland of land "Turn libbase into a component"

src/base/platform/semaphore.h

Index: src/base/platform/semaphore.h
diff --git a/src/base/platform/semaphore.h b/src/base/platform/semaphore.h
index 39029c83fc3b427d050421655bcfd6558b37f69d..31aeca3d9bd15568e42997ef3161e58d120121de 100644
--- a/src/base/platform/semaphore.h
+++ b/src/base/platform/semaphore.h
@@ -5,6 +5,7 @@
 #ifndef V8_BASE_PLATFORM_SEMAPHORE_H_
 #define V8_BASE_PLATFORM_SEMAPHORE_H_
 
+#include "src/base/base-export.h"
 #include "src/base/lazy-instance.h"
 #if V8_OS_WIN
 #include "src/base/win32-headers.h"
@@ -31,7 +32,7 @@
 // count reaches zero,  threads waiting for the semaphore blocks until the
 // count becomes non-zero.
 
-class Semaphore final {
+class V8_BASE_EXPORT Semaphore final {
  public:
   explicit Semaphore(int count);
   ~Semaphore();