test gnome-doc-tool in configure

configure.in

@@ -218,6 +218,8 @@ AC_ARG_WITH(htmldir, [  --with-htmldir=DIR      install path for html files],
 AC_DEFINE_UNQUOTED(GQ_HELPDIR, "$readmedir", [Location of documentation files])
 AC_DEFINE_UNQUOTED(GQ_HTMLDIR, "$htmldir", [Location of html documentation])
 
+AC_PATH_PROG(GNOME_DOC_TOOL, gnome-doc-tool)
+
 AC_SUBST(readmedir)
 AC_SUBST(htmldir)
 
@@ -469,6 +471,8 @@ Support:
 Documentation:
   Doxygen:       $DOXYGEN
   Formats:       $doxy_formats_report
+  doc-tool:      $GNOME_DOC_TOOL
+
 END
 
 cat config.report

doc/Makefile.am

@@ -8,13 +8,20 @@ help_DATA =
 EXTRA_DIST = docbook2html.sh docbook
 
 html/GuideIndex.html: docbook/GuideIndex.xml
-	rm -rf html; mkdir html && gnome-doc-tool html -o html $(srcdir)/docbook/GuideIndex.xml
+	rm -rf html; mkdir html
+	if [ -x "$(GNOME_DOC_TOOL)" ]; then \
+		"$(GNOME_DOC_TOOL)" html -o html $(srcdir)/docbook/GuideIndex.xml ; \
+	else \
+		echo "gnome-doc-tool not found, html is not built" ; \
+	fi
 
 html: html/GuideIndex.html
 
 install-data-hook: html
-	cd html; for f in * ; do $(INSTALL_DATA) "$$f" "$(DESTDIR)$(helpdir)/$$f" ; done
-	ln -s GuideIndex.html "$(DESTDIR)$(helpdir)/index.html"
+	if [ -x "$(GNOME_DOC_TOOL)" ]; then \
+		cd html; for f in * ; do $(INSTALL_DATA) "$$f" "$(DESTDIR)$(helpdir)/$$f" ; done; \
+		ln -s GuideIndex.html "$(DESTDIR)$(helpdir)/index.html" ; \
+	fi
 
 uninstall-hook:
 	rm "$(DESTDIR)$(helpdir)/"*