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/libseccomp-helper.h

@@ -0,0 +1,24 @@
+#include <seccomp.h>
+#include <stdint.h>
+
+#if (SCMP_VER_MAJOR < 2) || (SCMP_VER_MAJOR == 2 && SCMP_VER_MINOR < 5) ||     \
+    (SCMP_VER_MAJOR == 2 && SCMP_VER_MINOR == 5 && SCMP_VER_MICRO < 1)
+#error This package requires libseccomp >= v2.5.1
+#endif
+
+typedef enum {
+  HAKUREI_PREPARE_MULTIARCH = 1 << 0,
+  HAKUREI_PREPARE_CAN = 1 << 1,
+  HAKUREI_PREPARE_BLUETOOTH = 1 << 2,
+} hakurei_prepare_flag;
+
+struct hakurei_syscall_rule {
+  int syscall;
+  int m_errno;
+  struct scmp_arg_cmp *arg;
+};
+
+int32_t hakurei_prepare_filter(int *ret_p, int fd, uint32_t arch,
+                               uint32_t multiarch,
+                               struct hakurei_syscall_rule *rules,
+                               size_t rules_sz, hakurei_prepare_flag flags);