On Cygwin we have to use git-archive.exe as the target, otherwise
running 'make dist' does not compile git-archive in the current
directory. That may cause 'make dist' to fail on a clean source
tree that has never been built before.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>