Added copyright.

src/base/base.cmake

@@ -127,12 +127,10 @@ elseif (APPLE)
         )
 else()
     set(SOURCES_OS
+        src/base/io/Async.cpp
         src/base/io/json/Json_unix.cpp
         src/base/kernel/Platform_unix.cpp
         )
-    list(APPEND SOURCES_BASE
-        src/base/io/Async.cpp
-        )
 endif()