If interested in building custom toolchain using binutils,gcc,and a library[categorization based on library used] from source. Content below:

1. Build gcc with musl library
2. Build gcc with newlib library

1. Build gcc with musl library Follow link[1] this is similar to riscv_gnu_toolchain[2] where in simple steps you can build the toolchain.

2. Build gcc with newlib library

1. Create empty directory
2. Untar attached tar file to above folder.
3. Download sources from github git clone https://github.com/riscv/riscv-gcc.git git clone https://github.com/riscv/riscv-binutils-gdb git clone https://github.com/riscv/riscv-newlib
4. In runall.sh set $PREFIX to
5. run as ./runall.sh

Resource:[3]

If anything fails, please revert on list we will try solving it. [1]https://colematt.github.io/2018/11/26/building-llvm-for-riscv-cross-compilation.html

Links: [1]https://github.com/richfelker/musl-cross-make [2]https://github.com/riscv/riscv-gnu-toolchain [3]http://www.ifp.illinois.edu/~nakazato/tips/xgcc.html