sandbox/seccomp: resolve rules natively

This enables loading syscall filter policies from external cross-platform config files.

This also removes a significant amount of C code.

Signed-off-by: Ophestra <cat@gensokyo.uk>

sandbox/seccomp/presets_clone_backwards2.go

@@ -0,0 +1,7 @@
+//go:build s390 || s390x
+
+package seccomp
+
+/* Architectures with CONFIG_CLONE_BACKWARDS2: the child stack
+ * and flags arguments are reversed so the flags come second */
+const cloneArg = 1