Recommended toolchain for ethernet-v0.5

Hi,

What is the toolchain that you recommend for `git clone -b ethernet-v0.5 --recursive https://github.com/lowrisc/lowrisc-chip.git`.
The riscv-tools build that comes with clone has issue pulling binutils.2.26.tar.gz and thus build fails. The issue is consistent with all the releases that use binutils. Can you please point to riscv-tools that support ethernet-v0.5.

PS: I'm currently using ubuntu 18.04 with Vivado 2015.4. Bitstream generation and XSim simulation with default boot.mem have no issue. I'm looking forward to try bare metal hello example.

Thanks.

Use the ethernet-v0.5 clone command as the entry point and inspect the bundled riscv-tools build, focusing on the binutils.2.26.tar.gz fetch failure under Ubuntu 18.04. Compare the toolchain used by releases that build successfully, then document a supported riscv-tools/toolchain for the bare-metal hello example. Validate the recommendation against bitstream generation, XSim, and the hello example.

Written by the indexing model from the issue text.