MainGitBranch should read from Build.yml when set

Looking at the task that creates a build tag, for now the parameter is present for InvokeBuild, but it defaults to 'main' and does not let you set it in the yaml.

This should be updated, and other tasks using MainGitBranch should follow the same configuration.
The GitHub task I believe use a different key though, which is a duplicated...

Something to look into...

Start by tracing the task that creates a build tag and how InvokeBuild reads Build.yml, then find the other tasks using MainGitBranch. Check how the GitHub task names its equivalent setting; done means the configured branch is used consistently instead of the default and duplicated keys are understood or aligned.

Written by the indexing model from the issue text.