(from #30371)

In order to compile the cython files only using system-wide installed libraries the following has to be done (on Ubunutu 20.04, under WSL):

• Install dependencies:
  apt-get install liblinbox-dev libflint-arb-dev libhomfly-dev libgiac-dev libratpoints-dev libzn-poly-dev libbrial-dev libbrial-groebner-dev libatlas-base-dev

• Configure ARB by setting env variable ARB_LIBRARY to flint-arb.

• Install GAP:
  This would be apt-get install libgap-dev, but this requires Ubuntu 20.10: https://packages.ubuntu.com/groovy/libgap-dev and the old gap-dev didn't worked for me. So download libgap-dev, libgap7 and gap-libs manually from https://packages.ubuntu.com/groovy, and install them using sudo dpkg -i ./gap-libs_4.11.0-4_all.deb etc and sudo apt install -f

• Fix installation of ecl:
  After apt-get install ecl ecl is broken under WSL. To fix this, first run apt-get install libtool autoconf, then follow libsndfile fails to build on Ubuntu 20.04 with WSL rdp/ffmpeg-windows-build-helpers#452 (comment).
  Maybe it would also work to build ecl directly from code: https://common-lisp.net/project/ecl/static/manual/Building-ECL.html#Building-ECL (which is also a newer version). I also had the problem that ECL_WITH_LISP_FPE_BEGIN was not defined (probably because the version of ecl that I used was too old so that https://gitlab.com/embeddable-common-lisp/ecl/-/merge_requests/154 was not included.)

• Install maxima:
  apt-get install maxima-sage and register with ecl using sudo cp -f /usr/lib/ecl/maxima.fas /usr/lib/x86_64-linux-gnu/ecl-16.1.3/maxima.fas

• cysignals is broken, see Compilation failure cysignals#111.
  To fix this, remove all method bodies in python3.8/site-packages/cysignals/macros.h (relative to the venv).

CC: @tobiasdiez

Component: build

Issue created by migration from https://trac.sagemath.org/ticket/31347