Right now to build the pdf.so of zathura-mupdf, just
- apt-get source mupdf
- HAVE_MUJS := no in there
- rebuild libmupdf-dev with DEB_BUILD_OPTIONS=x-fpic
- dpkg -i libmupdf-dev...deb
- cd zathura-mupdf; remove "-lmujs" there
- make
- zathura --plugins-dir=zathura-mupdf test.pdf
And it renders lightning fast!!!