Makefile.am: fix dist-checksum target

Makefile.am

@@ -25,7 +25,7 @@ changelog:
 	  sed -e 's/^[^0-9]/ /' -e 's/^  *$$//' -e 's/^ \* 	/ /g' | \
 	  grep -v '^ \*$$' | uniq >| ChangeLog
 
-dist-checksum: $(DIST_TARGETS)
+dist-checksum: $(DIST_ARCHIVES)
 	rm -f *.md5 *.sha256
 	for sum in $(DIST_ARCHIVES); do \
 	  md5sum $$sum > $$sum.md5 && \