The "xorg-server-xwayland" package has become "xorg-xwayland" in Arch.
Our egl requirement was previously satisfied by xorg-server-xwayland's
dependency on libgl, which "xorg-xwayland" does not have. So add the
libegl dependency as well.
If unspecified, feature options are set to "auto", which means enabled only if
the required dependencies are found. In CI we don't want to miss compilation
errors because a dependency hasn't been found and code isn't built.
Leave FreeBSD out for now because it uses a subproject (haven't found a way to
make auto_features=enabled only apply to the toplevel project).
