Fix warnings from -DPLUGIN_PARTITION=NO, portably.

Also fix Spider's cmake.

sql/datadict.cc

@@ -151,7 +151,9 @@ Table_type dd_frm_type(THD *thd, char *path, LEX_CSTRING *engine_name,
     }
   }
 
-cont: __attribute__((unused));
+#ifdef WITH_PARTITION_STORAGE_ENGINE
+cont:
+#endif
   /* read the true engine name */
   {
     MY_STAT state;

sql/handler.cc

@@ -6201,7 +6201,9 @@ bool ha_table_exists(THD *thd, const LEX_CSTRING *db,
     DBUG_RETURN(TRUE);
   }
 
-retry_from_frm: __attribute__((unused));
+#ifdef WITH_PARTITION_STORAGE_ENGINE
+retry_from_frm:
+#endif
   char path[FN_REFLEN + 1];
   size_t path_len = build_table_filename(path, sizeof(path) - 1,
                                          db->str, table_name->str, "", 0);

storage/spider/CMakeLists.txt

@@ -73,7 +73,7 @@ IF(ORACLE_INCLUDE_DIR AND ORACLE_OCI_LIBRARY)
   ENDIF()
 ENDIF()
 
-IF(MSVC)
+IF(MSVC AND (TARGET spider))
   IF (CMAKE_BUILD_TYPE STREQUAL "Debug")
     ADD_CUSTOM_COMMAND(TARGET spider
                        POST_BUILD