From #33101 comment:3 :

"This was after a distclean. I had not explicitly installed lrslib, it was on the system. If I understand the config.log correctly, the system lrslib was not accepted by Sage. Yet, ptestlong runs the optional lrslib tests."

## ------------------------------------------------------- ##
## Checking whether SageMath should install SPKG lrslib... ##
## ------------------------------------------------------- ##
configure:30190: checking whether any of gmp flint is installed as or will be installed as SPKG
configure:30194: result: yes; install lrslib as well
configure:30296: no suitable system package found for SPKG lrslib

In this ticket, we add to the is_functional method a check corresponding to the check made in build/pkgs/lrslib/spkg-configure.m4 so that if lrslib is not picked up by sagemath at configuration/build time, then it is not picked up by sagemath at runtime or during doctests.

CC: @mwageringel @orlitzky

Component: packages: optional

Author: Sébastien Labbé, Markus Wageringel

Branch: 16e1b24

Reviewer: Matthias Koeppe

Issue created by migration from https://trac.sagemath.org/ticket/33167