commit 59294029f3d1 ("Capitalize package name and add capitalized tar-ball
prefix") had an unintended side effect: the cross build for Windows on
Linux no longer worked (as it set NAME=subsurface.exe).
Fixed this by introducing a TARGET variable that is derived from $(NAME).
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
ce46a60caf