msdos cross-compile follow-up bits

add missing make rule for ../win/share files to cross-pre.2020

adjust .travis.yml to use the new approach for building msdos target

sys/unix/hints/include/cross-post.2020

@@ -18,6 +18,7 @@ $(TARGETPFX)vidvesa.o : ../sys/msdos/vidvesa.c ../sys/msdos/portio.h \
 $(TARGETPFX)vidstub.o : ../sys/msdos/vidvesa.c ../sys/msdos/portio.h \
 		$(HACK_H)
 $(TARGETPFX)tile.o : tile.c
+$(TARGETPFX)recover.o : ../util/recover.c
 #
 #.PHONY: dospkg
 dospkg: $(GAMEBIN) $(TARGETPFX)recover.exe ../dat/nhtiles.bmp

sys/unix/hints/include/cross-pre.2020

@@ -283,7 +283,9 @@ ifdef WANT_WIN_CURSES
 $(TARGETPFX)%.o : $(PDCTOP)/pdcurses/%.c
 	$(TARGET_CC) $(PDCINCL) $(TARGET_CFLAGS) -o$@  $<
 endif  # WANT_WIN_CURSES
-
+# Rules for win/share files
+$(TARGETPFX)%.o : ../win/share/%.c
+	$(TARGET_CC) $(TARGET_CFLAGS) -o$@ $<
 # 
 # End of cross-compiling -PRE section
 #===============-=================================================