tree e8a0989d0e6ade55c6d56cd51dd1d27be6206cb2
parent b1d4b6a5955806c49755ab1a607f93995bfed25b
author Camilla Löwy <elmindreda@elmindreda.org> 1579460891 +0100
committer Camilla Löwy <elmindreda@elmindreda.org> 1579473811 +0100

Update OpenGL bits of build documentation slightly

This removes most references to GLU, replaces the legacy CMake cache
variables for OpenGL with the modern namespaced target and switches to
$() for command substitution.

Fixes #1580.

(cherry picked from commit d973acc123826666ecc9e6fd475682e3d84c54a6)