ELF binary type "0" not known. (while compiling buildworld on risc-v/qemu)

Hello,

I'm playing with compiling freebsd 13 (releng/13.0 2 days ago) and 
current (git HEAD as of today) on qemu-5.1.0/qemu-6.1.0 on risv64 
platform. The emulator invocation is:

qemu-system-riscv64 -machine virt -smp 8 -m 16G -nographic -device 
virtio-blk-device,drive=hd -drive 
file=FreeBSD-14.0-CURRENT-riscv-riscv64.qcow2,if=none,id=hd -device 
virtio-net-device,netdev=net -netdev user,id=net,hostfwd=tcp::2233-:22 
-bios /usr/lib/riscv64-linux-gnu/opensbi/generic/fw_jump.elf -kernel 
/usr/lib/u-boot/qemu-riscv64_smode/uboot.elf -object 
rng-random,filename=/dev/urandom,id=rng -device 
virtio-rng-device,rng=rng -nographic -append "root=LABEL=rootfs 
console=ttyS0"

and the host is Ubuntu 20.04.x LTS. Both qemu 5.1.0 and qemu 6.1.0 are 
compiled from, source, but both OpenSBI and u-boot for risc-v are Ubuntu 
packages provided (to accompany ubuntu provided qemu 4.2.1)

My issue while compiling both 13 and current is that compilation after 
some time fails with:

root@freebsd:/usr/src # time make -j8 buildworld > /tmp/build-j8-2.txt
ELF binary type "0" not known.
17784.134u 21388.907s 1:50:13.83 592.2% 30721+572k 10+2177io 0pf+0w

I'm curious if this is a know issue either in Qemu or in FreeBSD for 
risc-v or if I'm doing anything wrong here?

Thanks!
Karel