[documentation] 4.1.2. Compile self-test cases #22

According to "4.1.2. Compile self-test cases" of the documentation i need to download prebuild Nuclei RISC-V GNU toolchain and extract bin directory to e203_hbirdv2/riscv-tools/prebuilt_tools/prefix/bin. I made this an tried to launch "source regen.sh", but the result was "riscv-nuclei-elf-gcc: fatal error: cannot execute 'cc1': execvp: No such file or directory".
I can find cc1 binary file in the downloaded archive in gcc/libexec/gcc/riscv-nuclei-elf/10.2.0, but i don't understand how to make it visible to riscv-nuclei-elf-gcc.