To install riscv64-unknown-linux-gnu-libc, run the following command in macOS terminal (Applications->Utilities->Terminal)
sudo port install riscv64-unknown-linux-gnu-libc
To see what files were installed by riscv64-unknown-linux-gnu-libc, run:
port contents riscv64-unknown-linux-gnu-libc
To later upgrade riscv64-unknown-linux-gnu-libc, run:
sudo port selfupdate && sudo port upgrade riscv64-unknown-linux-gnu-libc
Reporting an issue on MacPorts Trac
The MacPorts Project uses a system called Trac to file tickets to report bugs and enhancement requests.
Though anyone may search Trac for tickets, you must have a GitHub account in order to login to Trac to create tickets.