Comment by chubot

Don't you need a pattern rule for %.d? GNU Make doesn't seem to come with this rule.

There is a profoundly ugly example here:

https://www.gnu.org/software/make/manual/html_node/Automatic...

    %.d: %.c
        @set -e; rm -f $@; \
         $(CC) -M $(CPPFLAGS) $< > $@.$$$$; \
         sed 's,\($*\)\.o[ :]*,\1.o $@ : ,g' < $@.$$$$ > $@; \
         rm -f $@.$$$$

I copied it into a running example here for anyone curious:

https://github.com/oilshell/blog-code/tree/master/dotd