Restructure repo around sing-box-rr package layout

sing-box-rr/experimental/libbox/pidfd_android.go

@@ -0,0 +1,19 @@
+package libbox
+
+import (
+	"os"
+	_ "unsafe"
+)
+
+// https://github.com/SagerNet/sing-box/issues/3233
+// https://github.com/golang/go/issues/70508
+// https://github.com/tailscale/tailscale/issues/13452
+
+//go:linkname checkPidfdOnce os.checkPidfdOnce
+var checkPidfdOnce func() error
+
+func init() {
+	checkPidfdOnce = func() error {
+		return os.ErrInvalid
+	}
+}