Set sensible defaults for Windows installations
Set sensible defaults for Windows installations

Non-packaged execution will need this to be overridden anyway, and it
avoids a surprise "Drop state data into the current working directory"
event.

Signed-off-by: Paul "TBBle" Hampson <220d126b3d70d9d7b0fda508e4cb236265bccc41@Pobox.com>

tonistiigi/buildkit_poc,tonistiigi/buildkit_poc