GNUmakefile: prevent build failure when ncurses headers are installed

apparently some parts of libterminfo use curses headers, and it was
reported that its build fails when ncurses headers are installed
systemwide, unless -I./libcurses is used (in which case our internal
headers take precedence).

closes sabotage-linux#30

Author: rofl0r

GNUmakefile

@@ -400,6 +400,9 @@ tic/%.o: tic/%.c
 libcurses/%.o: libcurses/%.c
 	$(CC) $(CPPFLAGS) -I./libcurses $(CFLAGS) -c -o $@ $<
 
+libterminfo/%.o: libterminfo/%.c
+	$(CC) $(CPPFLAGS) -I./libcurses $(CFLAGS) -c -o $@ $<
+
 libmenu/%.o: libmenu/%.c
 	$(CC) $(CPPFLAGS) -I./libcurses -I./libmenu $(CFLAGS) -c -o $@ $<
 
@@ -410,6 +413,7 @@ libform/%.o: libform/%.c
 	$(CC) $(CPPFLAGS) -I./libcurses -I./libmenu -I./libform $(CFLAGS) -c -o $@ $<
 
 ifeq ($(ALLPIC),1)
+
 $(CU_LOBJS): $(CU_OBJS)
 libcurses/%.lo: libcurses/%.o
 	$(LN) -sf $(notdir $<) $@
@@ -434,7 +438,7 @@ libcurses/%.lo: libcurses/%.c
 	$(CC) $(CPPFLAGS) -I./libcurses $(CFLAGS) $(PIC) -c -o $@ $<
 
 libterminfo/%.lo: libterminfo/%.c
-	$(CC) $(CPPFLAGS) $(CFLAGS) $(PIC) -c -o $@ $<
+	$(CC) $(CPPFLAGS) -I./libcurses $(CFLAGS) $(PIC) -c -o $@ $<
 
 libpanel/%.lo: libpanel/%.c
 	$(CC) $(CPPFLAGS) -I./libcurses -I./libpanel $(CFLAGS) $(PIC) -c -o $@ $<