Apparently, generic builder sets `nullglob`, disappearing any flags containing square brackets
not resolving to file names (e.g. `mesonFlags = [ "-Dgl_winsys=[x11,wayland]" ];`). This caused
the `gl_winsys` flag default to `auto` and, since we were missing `wayland-protocols`, Wayland
support was not built.
Fortunately, Meson also supports simple array notation without square brackets, so we can use
that. No need to wait for `_structuredAttrs`.
We also no longer set `gl_platform` flag, since passing the default auto value is redundant.
5a139f0e7d