MDEV-8962 TokuDB tries to build on OS X, even when disabled in compile flag

first add tokudb plugin (MYSQL_ADD_PLUGIN) then add dependent
targets (ADD_SUBDIRECTORY(ft-index))

storage/tokudb/CMakeLists.txt

@@ -9,7 +9,15 @@ int main() { return 0; }
 " TOKUDB_OK)
 ENDIF()
 
-IF(NOT TOKUDB_OK OR PLUGIN_TOKUDB STREQUAL "NO")
+IF(NOT TOKUDB_OK)
+  RETURN()
+ENDIF()
+
+SET(TOKUDB_SOURCES ha_tokudb.cc)
+MYSQL_ADD_PLUGIN(tokudb ${TOKUDB_SOURCES} STORAGE_ENGINE MODULE_ONLY
+    LINK_LIBRARIES ${ZLIB_LIBRARY} stdc++)
+
+IF(NOT TARGET tokudb)
   RETURN()
 ENDIF()
 
@@ -77,10 +85,8 @@ INCLUDE_DIRECTORIES(${CMAKE_CURRENT_BINARY_DIR}/ft-index)
 INCLUDE_DIRECTORIES(${CMAKE_CURRENT_BINARY_DIR}/ft-index/buildheader)
 INCLUDE_DIRECTORIES(${CMAKE_CURRENT_BINARY_DIR}/ft-index/portability)
 
-SET(TOKUDB_PLUGIN_DYNAMIC "ha_tokudb")
-SET(TOKUDB_SOURCES ha_tokudb.cc)
-MYSQL_ADD_PLUGIN(tokudb ${TOKUDB_SOURCES} STORAGE_ENGINE MODULE_ONLY
-    LINK_LIBRARIES tokufractaltree_static tokuportability_static ${ZLIB_LIBRARY} stdc++)
+TARGET_LINK_LIBRARIES(tokudb tokufractaltree_static tokuportability_static)
+
 SET(CMAKE_MODULE_LINKER_FLAGS_RELEASE "${CMAKE_MODULE_LINKER_FLAGS_RELEASE} -flto -fuse-linker-plugin")
 SET(CMAKE_MODULE_LINKER_FLAGS_RELWITHDEBINFO "${CMAKE_MODULE_LINKER_FLAGS_RELWITHDEBINFO} -flto -fuse-linker-plugin")