xfwm4 master fails to build on debian stretch: https://buildbot.xfce.alteroot.org/job/xfwm4/nodes=Debian/34/console
It happens since commit https://git.xfce.org/xfce/xfwm4/commit/?id=1311eecd33e173ac64ebd48e7a9cf37452d7dc1c ( compositor: Use epoxy to check for glx support).
The epoxy_has_glx function exists since libepoxy 1.4.0 ( https://github.com/anholt/libepoxy/commit/d94b9c28b53b1bf99f4a497486af681d8bc95d95 ) but Debian Stretch provides 1.3.2.
xfwm4 requires libepoxy 1.0.
A solution is to bump the minimum libepoxy version in configure.ac.in
Alternatively, we could revert that commit if it is problematic, it's mostly cosmetic...
In this case, revert the commit is a good idea
Olivier Fourdan referenced this bugreport in commit 61baa5fda137733000d106cddad1f52f9e99fba0
Revert "compositor: Use epoxy to check for glx support"