add ~riscv keyword
Looks good on riscv USE tests started on Thu Nov 3 14:39:31 -00 2022 FEATURES=' test' USE='' succeeded for =www-servers/boa-0.94.14_rc21-r2 USE='-doc' succeeded for =www-servers/boa-0.94.14_rc21-r2
riscv done all arches done