Add home dir configuration on windows (like unix)

What does this MR do?

Fix windows "homedir", like unix version do

Why was this MR needed?

Without this, gitlab-runner search for config.toml in current directory instead of ~/.gitlab-runner

What's the best way to test this MR?

Compare gitlab-runner list on windows/linux:

• On Windows:
  • ./gitlab-runner-windows-amd64.exe including this patch
  • gitlab-runner.exe downloaded from gitlab)
    
• On linux:

gitlab-runner list
Runtime platform                                    arch=amd64 os=linux pid=199982 revision=ece86343 version=13.5.0
Listing configured runners                          ConfigFile=/home/moi/.gitlab-runner/config.toml

What are the relevant issue numbers?

Nothing found 🙇

Workaround

set environnement variable CONFIG_FILE to %USERPROFILE%\.gitlab-runner\config.toml work to 😆