seccomp: add riscv_flush_icache to allow list

This system call is harmless because it only enforces ordering between stores
and instruction cache fetch.

fixed #24991
Related: https://github.com/felixonmars/archriscv-packages/issues/1840

Signed-off-by: Celeste Liu <CoelacanthusHex@gmail.com>
(cherry picked from commit 09925036cf)

src/shared/seccomp-util.c

@@ -334,6 +334,7 @@ const SyscallFilterSet syscall_filter_sets[_SYSCALL_FILTER_SET_MAX] = {
                 "pause\0"
                 "prlimit64\0"
                 "restart_syscall\0"
+                "riscv_flush_icache\0"
                 "rseq\0"
                 "rt_sigreturn\0"
                 "sched_getaffinity\0"