Changes made to sys.config.src are not taking effect under windows

[helloyan]

use rebar3 which build with relx

Enviroment：
rebar 3.20.0 on Erlang/OTP 24 Erts 12.3.2.1
OS Name: Microsoft Windows 10 专业版
OS Version: 10.0.19042 N/A Build 19042

When I use the config/sys.config.src file and the release command, I can see the sys.config.src file in rel/appname/release/x.x.x/sys.config.src, but the configuration changes don't take effect.

sys.config.src
[{kernel, [{logger, [{handler, default, undefined}]}]}].

The configuration changes take effect under CentOS 7, and the sys.config file is generated after running '_build/***/bin/appname console', but the file isn't generated on Windows systems.

erlang/rebar3#2775