Execution results consist of non-ascii characters are garbled on Windows

Summary

Execution result of script on gitlab-runner consist of non-ascii characters (Japanese in my case) are garbled when output results.

Steps to reproduce

1. For example, execute the following script on gitlab-runner on Windows PC.(7z command is not installed.)

stages:
  - install
  - test

install:
  stage: install
  script:
    - 7z x test.zip

Actual behavior

7z : �p�� '7z' �́A�R�}���h���b�g�A�֐��A�X�N���v�g �t�@�C���A�܂��͑����”\��
�v���O�����̖��O�Ƃ��ĔF�������܂����B���O���������L�q�����Ă��邱�Ƃ��m�F���A
�p�X���܂܂��Ă����ꍇ�͂��̃p�X�����������Ƃ��m�F���Ă����A�Ď��s���Ă�������
�B
�����ꏊ C:\Windows\TEMP\build_script476614695\script.ps1:185 ����:1
+ 7z x $PACKAGE_NAME
+ ~~
    + CategoryInfo          : ObjectNotFound: (7z:String) [], CommandNotFoundE 
   xception
    + FullyQualifiedErrorId : CommandNotFoundException

Expected behavior

We expect that the output command result with not garbled.

Relevant logs and/or screenshots

job log

$ 7z x test.zip
7z : �p�� '7z' �́A�R�}���h���b�g�A�֐��A�X�N���v�g �t�@�C���A�܂��͑����”\��
�v���O�����̖��O�Ƃ��ĔF�������܂����B���O���������L�q�����Ă��邱�Ƃ��m�F���A
�p�X���܂܂��Ă����ꍇ�͂��̃p�X�����������Ƃ��m�F���Ă����A�Ď��s���Ă�������
�B
�����ꏊ C:\Windows\TEMP\build_script476614695\script.ps1:185 ����:1
+ 7z x $PACKAGE_NAME
+ ~~
    + CategoryInfo          : ObjectNotFound: (7z:String) [], CommandNotFoundE 
   xception
    + FullyQualifiedErrorId : CommandNotFoundException

Environment description

config.toml contents

concurrent = 1
check_interval = 0

[session_server]
  session_timeout = 1800

[[runners]]
  name = "xxxxxxxxxxxxxxxxxxxxxxxx"
  url = "https://xxxxxxxxxxxxxxxxx/"
  token = "xxxxxxxxxxxxxxxx"
  executor = "shell"
  shell = "powershell"
  [runners.custom_build_dir]
  [runners.cache]
    [runners.cache.s3]
    [runners.cache.gcs]
  [runners.custom]
    run_exec = ""

Used GitLab Runner version

Running with gitlab-runner 12.1.0 (de7731dd)
  on xxxxxxxx
Using Shell executor...