make pdf depend on png

diff --git a/Makefile b/Makefile
index 999f4c90454937be4b44c837a3d54e093e62e647..17745a12e6a065dfeee5c2846c80737d4f357fe7 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -20,6 +20,8 @@ hourglass-$(VERSION).tgz: $(BIN) $(OTHER) $(DOCS)
 %.html: %.adoc
        asciidoctor $< > $@
 
+hourglass-guide.pdf: $(wildcard *.png)
+
 %.pdf: %.adoc
        asciidoctor-pdf $< > $@