bugfix: disabling partitioning in already built tree

that didn't quite work, WITH_PARTITION_STORAGE_ENGINE
was not undefined

cmake/plugin.cmake

@@ -104,6 +104,7 @@ MACRO(MYSQL_ADD_PLUGIN)
   ELSE()
     SET(with_var "WITH_${plugin}")
   ENDIF()
+  UNSET(${with_var} CACHE)
   
   IF(NOT ARG_DEPENDENCIES)
     SET(ARG_DEPENDENCIES)
@@ -218,8 +219,6 @@ MACRO(MYSQL_ADD_PLUGIN)
     ENDIF()
     ADD_DEPENDENCIES(${target} GenError ${ARG_DEPENDENCIES})
 
-    UNSET(${with_var} CACHE)
-
     SET_TARGET_PROPERTIES(${target} PROPERTIES 
       OUTPUT_NAME "${ARG_MODULE_OUTPUT_NAME}")  
     # Install dynamic library