First make sure your current user can write to /opt/riscv64b:
sudo mkdir /opt/riscv64b
sudo chown $USER: /opt/riscv64b
Then run:
bash build-all.sh
This builds and installs binutils, gcc, newlib, riscv-pk, and riscv-isa-sim.
It will also install <rvintrin.h> and run some simple tests on the tools.
Finally, running the B-extension tests:
cd ../tests
bash run.sh