clone-pack: use create_symref() instead of raw symlink.
clone-pack: use create_symref() instead of raw symlink.

This was the last instance of symlink() in coreish part.

Signed-off-by: Junio C Hamano <dc50d1021234060e53ec42a77d526afa2fe07479@cox.net>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git