gdk/wayland/cursor/os-compatibility: fix build when memfd_create is not available
When building for homebrew/linuxbrew on Ubuntu 16.04, memfd_create() is not available and causes the build to fail.
This adds a proper check for the function.
When building for homebrew/linuxbrew on Ubuntu 16.04, memfd_create() is not available and causes the build to fail.
This adds a proper check for the function.