Build fails

To make it short:

$ git submodule update --init --recursive
fatal: No url found for submodule path 'src/linux' in .gitmodules
$ make initramfs-purism-librem5.gz
MAKE  initramfs/bin/busybox
make[1]: Entering directory '/home/foo/jumpdrive/src/busybox'
make[1]: *** No targets specified and no makefile found.  Stop.
make[1]: Leaving directory '/home/foo/jumpdrive/src/busybox'
make: *** [Makefile:76: initramfs/bin/busybox] Error 2