nwztools: fix Makefile

Seems like newer versions of mingw will sponteanously add a .exe suffix to
the output path if it doesn't have one, for example mingw-gcc -o scsitool bla
will actually create scsitool.exe and of course this breaks my release script.
Fix this by explicitely adding the .exe to avoid any problem

Change-Id: Ic8019b968b532b2ca612ba0c03977a96c22cee01
1 file changed