fix for out-of-source-tree builds

doc/Makefile.am

@@ -63,7 +63,7 @@ dist-hook : $(MAN_DOC) $(HTML_DOC)
 # the following Bash snippet is used to automatically generate an alphabetical list included by index.adoc:
 __pagelist:
 	echo >__pagelist
-	for adocfile in $$(ls *.adoc); do \
+	for adocfile in $(ASCIIDOC_DOC); do \
         if [ "$${adocfile}" != "index.adoc" ]; then \
 		    noext=$${adocfile//.adoc/}; \
 		    echo "* xref:$${adocfile}[$${noext}]" >> __pagelist; \