add ~riscv keyword
Looks good on riscv USE tests started on Wed Nov 2 13:49:07 -00 2022 FEATURES=' test' USE='' succeeded for =net-p2p/airdcpp-webclient-2.11.2 USE='nat-pmp -tbb webui' succeeded for =net-p2p/airdcpp-webclient-2.11.2 FEATURES=' test' USE='' succeeded for =www-apps/airdcpp-webui-2.11.2 USE='' succeeded for =www-apps/airdcpp-webui-2.11.2
riscv done all arches done