disable -Werror in MYSQL_MAINTAINER_MODE=ON until all plugins are ready

only activate it on MYSQL_MAINTAINER_MODE=ERRON

cmake/maintainer.cmake

@@ -35,7 +35,7 @@ IF(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
 ENDIF()
 
 # Turn on Werror (warning => error) when using maintainer mode.
-IF(MYSQL_MAINTAINER_MODE MATCHES "ON")
+IF(MYSQL_MAINTAINER_MODE MATCHES "ERR")
   SET(MY_C_WARNING_FLAGS "${MY_C_WARNING_FLAGS} -DFORCE_INIT_OF_VARS -Werror")
   SET(MY_CXX_WARNING_FLAGS "${MY_CXX_WARNING_FLAGS} -DFORCE_INIT_OF_VARS -Werror")
 ENDIF()