Fix cmake build on AIX.

The --version-script linker option is not supported by the linker on AIX systems

CMakeLists.txt

@@ -185,7 +185,7 @@ endif()
 if(UNIX)
     # On unix-like platforms the library is almost always called libz
    set_target_properties(zlib zlibstatic PROPERTIES OUTPUT_NAME z)
-   if(NOT APPLE)
+   if(NOT APPLE AND NOT(CMAKE_SYSTEM_NAME STREQUAL AIX))
      set_target_properties(zlib PROPERTIES LINK_FLAGS "-Wl,--version-script,\"${CMAKE_CURRENT_SOURCE_DIR}/zlib.map\"")
    endif()
 elseif(BUILD_SHARED_LIBS AND WIN32)