[seL4] question about SEL4PROJ /camkes-arm-vm-manifest

Hi, all I try to build a TK1 ARM VMM image from the source code SEL4PROJ/camkes-vm-manifest in GitHub. However, I can not compile it. I get errors when the compiler tries to build "camkes-accelerator" . I don't put any new code yet. I just: 1) repo init the url ; 2) repo sync; 3) make tk1_vm_defconfig; and 4) make. Did I do something wrong here? thanks Peng