Package exists on Arch and Fedora according to https://repology.org/project/coxeter/versions; they install coxeter in a compatible way, i.e., headers with the prefix coxeter/.

In this ticket we change the includes in src/sage/libs/coxeter3/decl.pxd to use the prefix coxeter/, which allows us to get rid of include_dirs in src/module_list.py:

    OptionalExtension('sage.libs.coxeter3.coxeter',
              sources = ['sage/libs/coxeter3/coxeter.pyx'],
              language="c++",
              include_dirs = [os.path.join(SAGE_INC, 'coxeter')],
              package = 'coxeter3'),

This simplifies the work in #29720.

CC: @tscrim @dimpase @orlitzky @antonio-rojas @isuruf

Component: build: configure

Keywords: sd109

Author: Matthias Koeppe

Branch/Commit: 1497f3f

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/29721