Rebuilding everything

Hi, i'm currently [making a package](https://github.com/HuayraLinux/pkg-arduino-avr-core) for a debian based distribution (and hoping to make that package go to debian itself) and when possible packaging binaries is a no-no.

Under the bootloaders folder there are a lot of `.hex` files that i don't know how to rebuild (missing USB_ID variable on the makefile).

Is documented anywhere how to rebuild all the core? I've downloaded the old versions of lufa and rebuilt most of the things that are here.

Related question. Is everything in the core needed? For example the bootloader `Leonardo-prod-firmware-2012-04-26.hex`

Start with the bootloaders folder, its .hex files, and the Makefile reference to the missing USB_ID variable. Review the older LUFA sources mentioned in the issue and determine how the core and bootloader artifacts are rebuilt. Done means the rebuild process and the role of files such as Leonardo-prod-firmware-2012-04-26.hex are documented.

Written by the indexing model from the issue text.