How to use pre_clone_script in config.toml?

I'd like to configure a runner on my local computer which runs on Windows10.

I could successfully set up a service and compile my project if I execute the runner manually in a console using "run" option.

But I can't use it as a service because it can't find git.exe.

Indeed I added the path to git.exe in my user PATH environment variable but not in the system PATH environment variable (and I d'like to keep it as is).

So I though I could use pre_clone_script option in my config.toml file to execute a command like

set PATH=%PATH%;%LOCALAPPDATA%\Atlassian\SourceTree\git_local\bin

But I can't figure out the proper way to set it.

Can someone show my the correct syntax?