makefile: generate depfiles for the correct object files

The depfiles were completely ineffective.

Now this is fixed.

The -MT argument sets the path for the dependenency root. By default it is set
only to a filename, and thus does not include the full path of the file.

Makefile

@@ -117,7 +117,7 @@ $(LIBFT):
 
 %.o: %.c
 	$(CC) -c $(CFLAGS) $(IFLAGS) -o $*.o $*.c
-	$(CC) -MM $(CFLAGS) $(IFLAGS) $*.c > $*.d
+	$(CC) -MM $(CFLAGS) $(IFLAGS) -MT $*.o $*.c > $*.d
 
 clean:
 	+$(MAKE) -C $(LIBFTDIR) clean

tests/Makefile

@@ -44,7 +44,7 @@ run: $(run_tests)
 
 %.o: %.c
 	$(CC) -c $(CFLAGS) $(IFLAGS) -o $*.o $*.c
-	$(CC) -MM $(CFLAGS) $(IFLAGS) $*.c > $*.d
+	$(CC) -MM $(CFLAGS) $(IFLAGS) -MT $*.o $*.c > $*.d
 
 test_%: %.o $(objs)
 	$(CC) $(CFLAGS) -rdynamic -o $@ $*.o $(objs) $(LINCLUDE) $(LDLIBS)