Usage: Build this like a normal iPXE binary (see also https://ipxe.org/download):
git checkout v1.20.1-xnba
make bin-x86_64-efi/ipxe.efi
Then copy the resulting binary to /tftpboot/xcat/:
mv bin-x86_64-efi/ipxe.efi /tftpboot/xcat/xnba_1.20.1.efi
cd /tftpboot/xcat
chmod 644 xnba_1.20.1.efi
mv xnba.efi xnba_1.0.3.efi
ln -s xnba_1.20.1.efi xnba.efi