Allow user to turn off PowerShell -NoProfile

Overview

According to the go code, and my experimentation, gitlab-runner launches powershell with the -NoProfile parameter, thus making it impossible to use the profile feature.

What was the design decision regarding disabling PowerShell profiles when launching the shell in the windows runner?

Proposal

Add a feature toggle to allow users to explicitly not add -NoProfile when starting a new PowerShell shell. By default, we should always add -NoProfile but only remove it when the user explicitly does turns this on. We can either do this via an environment variable or at a config.toml level