Just noticed that the spooles package maintained by debian is up to date and has the mentioned I2Ohash and many other bug fixes and corrections. So definitely I recommend to build CalculiX with system libraries.
see the changelog found on the source package matained by debian (11):
“http://deb.debian.org/debian/pool/main/s/spooles/spooles_2.2-14.debian.tar.xz”