To install gnu toolchain the efabless website redirects to a risc v github page. RISC-V GNU Compiler Toolchain This is the RISC-V C and C++ cross-compiler. It supports two build modes: a generic ELF/Newlib toolchain and a more sophisticated Linux-ELF/glibc toolchain. I was able to download neither of them. git clone waits for half an hour and times out. Tried multiple times. Will be waiting for the updated information.

Can't you install the toolchain through your distribution? On Debian i was able to install it through the package manager. You may need to adjust the example makefile for the firmware but thats it.

People can do many things on their own. We don't want to discuss here. We will try to follow what efabless is recommending.