[5.4] Enable symlink support explicitly

[stevapple]

Enable symlink support explicitly

This is a cherry-pick of commit 5f80bd7 from main.

Motivation:

enable git symlink support for Windows

Modifications:

pass core.symlinks=true to git clone operations

Result:

repositories cloned by SwiftPM will have core.symlinks set to true

[tomerd]

thanks for opening this @stevapple, we will keep an eye out for if/when we do a 5.4 dot release

[tomerd]

@swift-ci please smoke test

[tomerd]

@swift-ci test

[abertelrud]

LGTM

[tomerd]

@stevapple to get this into 5.4 sooner, can you make this change windows only (i.e. behind an #if)? this will allow it to go out sooner in a linux/windows only dot release

[stevapple]

@tomerd Though the initial purpose is for Windows, I suppose that this change is also useful for Linux and Darwin machines where the user unexpectedly disabled symlink support systemwide.

[tomerd]

@tomerd Though the initial purpose is for Windows, I suppose that this change is also useful for Linux and Darwin machines where the user unexpectedly disabled symlink support systemwide.

@stevapple correct, which is why we have merged the main PR without such conditionals. For 5.4 tho, if we want to get this sooner on a non-darwin patch release, we should conditionalize it, or if you prefer to wait until (and if) there is a cross platform patch release that is okay with me too

[tomerd]

@swift-ci please test