Fix:

/usr/bin/install: illegal option -- D

https://github.com/ekenberg/quotatool/issues/30
Reverts https://github.com/ekenberg/quotatool/commit/5529c8084a06d4d95905f76e47d2621564876081
--- Makefile.orig	2024-07-24 04:23:51.000000000 -0500
+++ Makefile	2024-08-15 04:51:31.000000000 -0500
@@ -65,8 +65,8 @@
 men   :=   $(wildcard $(srcdir)/man/*)
 install: $(prog)
 	$(NORMAL_INSTALL)
-	$(INSTALL_PROGRAM) -D $(srcdir)/$(prog) $(DESTDIR)$(sbindir)/$(prog)
-	$(foreach man,$(men),$(INSTALL_DATA) -D $(man) $(DESTDIR)$(mandir)/man$(subst .,,$(suffix $(man)))/$(notdir $(man)))
+	$(INSTALL_PROGRAM) $(srcdir)/$(prog) $(DESTDIR)$(sbindir)/$(prog)
+	$(foreach man,$(men),$(INSTALL_DATA) $(man) $(DESTDIR)$(mandir)/man$(subst .,,$(suffix $(man)))/$(notdir $(man)))
 
 uninstall:
 	$(NORMAL_UNINSTALL)