Well, I done did it. 2011 Apple MacBook Air 4,2 support added in Libreboot. UNTESTED, so pushed to WIP branch. I'm waiting for the one I ordered to arrive.
Patch:
It compiles. It auto-downloads me.bin by first downloading an Apple EFI firmware update as a .dmg file from Apple, directly. The .dmg file is LZMA compressed inside, so lbmk uses 7z from p7zip recursively until it finds me.bin inside (bruteforced with me_cleaner on each file until neutered me.bin is created).