/usr/bin/riscv64-linux-gnu-gdc is in gdc-riscv64-linux-gnu 4:8-20180321-2ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/bin/riscv64-linux-gnu-gdc-8
/usr/bin/riscv64-linux-gnu-gdc-8