build: Use mv instead of «cp -p»

There's no point in preserving the file metadata if we are going to
overwrite it from a shell redirection.

scripts/Makefile.am

@@ -162,8 +162,8 @@ endif
 
 # Ideally we'd use 'sed -i', but unfortunately that's not portable.
 install-data-hook:
-	cp -p $(DESTDIR)$(perllibdir)/Dpkg.pm \
-	      $(DESTDIR)$(perllibdir)/Dpkg.pm.tmp
+	mv $(DESTDIR)$(perllibdir)/Dpkg.pm \
+	   $(DESTDIR)$(perllibdir)/Dpkg.pm.tmp
 	$(do_perl_subst) <$(DESTDIR)$(perllibdir)/Dpkg.pm.tmp \
 	                 >$(DESTDIR)$(perllibdir)/Dpkg.pm
 	rm -f $(DESTDIR)$(perllibdir)/Dpkg.pm.tmp

scripts/mk/Makefile.am

@@ -11,7 +11,8 @@ do_path_subst = $(AM_V_GEN) \
                 sed -e "s:dpkg_datadir[[:space:]]*=[[:space:]]*[^[:space:]]*:dpkg_datadir = $(pkgdatadir):"
 
 install-data-hook:
-	cp -p $(DESTDIR)$(pkgdatadir)/default.mk $(DESTDIR)$(pkgdatadir)/default.mk.tmp
+	mv $(DESTDIR)$(pkgdatadir)/default.mk \
+	   $(DESTDIR)$(pkgdatadir)/default.mk.tmp
 	$(do_path_subst) <$(DESTDIR)$(pkgdatadir)/default.mk.tmp \
 			 >$(DESTDIR)$(pkgdatadir)/default.mk
 	rm -f $(DESTDIR)$(pkgdatadir)/default.mk.tmp