executor, sys/linux, pkg: enable syz_kvm_setup_cpu for riscv64 #18694

Job	Run time
race	7m 15s
old	7m 20s
dashboard	2m 2s
race_dashboard	2m 43s
build	4m 9s
aux	4m 43s
gvisor	4m 4s
arch (presubmit_arch_freebsd)	6m 37s
arch (presubmit_arch_linux)	10m 3s
arch (presubmit_arch_darwin)	3m 56s
arch (presubmit_arch_openbsd)	3m 53s
arch (presubmit_arch_netbsd)	3m 59s
arch (presubmit_arch_windows)	3m 47s
arch (presubmit_arch_executor)	3m 21s
	1h 7m 52s

Provide feedback