You can replace the bin/mkws script with a Plan9 mk file to get incremental builds:
#!/usr/local/plan9/bin/mk -f URL=//example.com SHARE=share LANG=en_US.UTF-8 THEMEFILES=$SHARE/l.upphtml\ $SHARE/s.uppcss\ TPLFILES=`{find . ! -name "l.upphtml" -name "*.upphtml" | cut -c3-} HTMLFILES=${TPLFILES:%.upphtml=%.html} $URL:V: sitemap.xml $HTMLFILES %.html:Q: %.upphtml $THEMEFILES >&2 echo Making $target pp $SHARE/l.upphtml ${target%.html}.upphtml $url > $target sitemap.xml:Q: $HTMLFILES $SHARE/sitemap.uppxml >&2 echo Making $target pp $SHARE/sitemap.uppxml $url > $target clean:VQ: Removing "$HTMLFILES" sitemap.xml rm -f $HTMLFILES sitemap.xml