Inkscape's CLI has changed in version 1.0

https://wiki.inkscape.org/wiki/index.php/Release_notes/1.0#Command_Line

Makefile

@@ -60,7 +60,7 @@ clean:
 	pdf2swf $< && chmod -x $@
 
 %.pdf:%.svg
-	inkscape -f $< --export-pdf=$@
+	inkscape --export-type=pdf -o $@ $<
 
 %.pdf:%.odg
 	libreoffice --headless --convert-to pdf $< --outdir odgs