git-clone-to-dir.sh fails by default on newer git versions

[crummel]

Git has disallowed the file transport by default now so git-clone-to-dir.sh fails with fatal: transport 'file' not allowed. The solution is either git config --global protocol.file.allow always (for all clones on the machine) or git -c protocol.file.allow=always clone <other stuff as usual> (for the individual clone command).

[MichaelSimons]

[Triage] @crummel - please check if this affects the 6.0+ tarball creation infrastructure. If this only affects 3.1 we won't fix this given its EOL is December.

[MichaelSimons]

[Triage] Per @crummel, this only affects 3.1 which is EOL shortly so we won't fix this.

[crummel]

Also showing up in dotnet/aspnetcore#46174, we do need to fix this.

[wtgodbe]

@crummel any ETA on fixing this? Our source-build job is failing very frequently right now, it's causing a lot of disruption. Want to know if we should just disable it in the meantime.