The BootLoaderSpec (BLS) defines a scheme where different bootloaders can
share a format for boot items and a configuration directory that accepts
these common configurations as drop-in files [0].
Generate BLS snippets at build time that can be copied on kernel install,
so bootloaders can parse to create menu entries using this information.
[0]: https://www.freedesktop.org/wiki/Specifications/BootLoaderSpec/
Signed-off-by: Peter Jones <pjones@redhat.com>