Fix cmake warning caused by 751ebe44

CMake Warning (dev) at cmake/plugin.cmake:288 (GET_TARGET_PROPERTY):
  Policy CMP0045 is not set: Error on non-existent target...

Also, fix condition argument in ADD_FEATURE_INFO. It is not a string
but boolean

cmake/plugin.cmake

@@ -257,15 +257,20 @@ MACRO(MYSQL_ADD_PLUGIN)
     INSTALL_MYSQL_TEST("${CMAKE_CURRENT_SOURCE_DIR}/mysql-test/" "plugin/${subpath}")
   ENDIF()
 
-  GET_TARGET_PROPERTY(plugin_type ${target} TYPE)
-  STRING(REGEX REPLACE "_LIBRARY$" "" plugin_type ${plugin_type})
-  STRING(REGEX REPLACE "^NO$" "" plugin_type ${plugin_type})
+  IF(TARGET ${target})
+    GET_TARGET_PROPERTY(plugin_type ${target} TYPE)
+    STRING(REPLACE "_LIBRARY" "" plugin_type ${plugin_type})
+    SET(have_target 1)
+  ELSE()
+    SET(plugin_type)
+    SET(have_target 0)
+  ENDIF()
   IF(ARG_STORAGE_ENGINE)
-    ADD_FEATURE_INFO(${plugin} PLUGIN_${plugin} "Storage Engine ${plugin_type}")
+    ADD_FEATURE_INFO(${plugin} ${have_target} "Storage Engine ${plugin_type}")
   ELSEIF(ARG_CLIENT)
-    ADD_FEATURE_INFO(${plugin} PLUGIN_${plugin} "Client plugin ${plugin_type}")
+    ADD_FEATURE_INFO(${plugin} ${have_target} "Client plugin ${plugin_type}")
   ELSE()
-    ADD_FEATURE_INFO(${plugin} PLUGIN_${plugin} "Server plugin ${plugin_type}")
+    ADD_FEATURE_INFO(${plugin} ${have_target} "Server plugin ${plugin_type}")
   ENDIF()
   ENDIF(NOT WITHOUT_SERVER OR ARG_CLIENT)
 ENDMACRO()