[build] Add dependency of generated files upon Makefile

Ensure that any generated files (such as DER forms of X.509
certificates) are rebuilt if the Makefile changes.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/Makefile.housekeeping

 $(shell $(ECHO) "$(EMBED)" > $(EMBEDDED_LIST))
 endif
 
-$(EMBEDDED_LIST) :
+$(EMBEDDED_LIST) : $(MAKEDEPS)
 
 VERYCLEANUP	+= $(EMBEDDED_LIST)
 
 $(shell $(ECHO) "$(TRUST)" > $(TRUSTED_LIST))
 endif
 
-$(TRUSTED_LIST) :
+$(TRUSTED_LIST) : $(MAKEDEPS)
 
 VERYCLEANUP	+= $(TRUSTED_LIST)
 
 $(shell $(ECHO) "$(CERT)" > $(CERT_LIST))
 endif
 
-$(CERT_LIST) :
+$(CERT_LIST) : $(MAKEDEPS)
 
 VERYCLEANUP += $(CERT_LIST)
 
 $(shell $(ECHO) "$(PRIVKEY)" > $(PRIVKEY_LIST))
 endif
 
-$(PRIVKEY_LIST) :
+$(PRIVKEY_LIST) : $(MAKEDEPS)
 
 VERYCLEANUP += $(PRIVKEY_LIST)
 
 $(shell $(ECHO) "$(BLIB_OBJS)" > $(BLIB_LIST))
 endif
 
-$(BLIB_LIST) :
+$(BLIB_LIST) : $(MAKEDEPS)
 
 VERYCLEANUP	+= $(BLIB_LIST)