Fix Switch OTA launcher self-update via a bootstrap NRO.

A running launcher cannot replace its own NRO on sdmc/FAT; stage the new
binary and chainload a tiny helper from romfs to swap it in before loading
the game.

native/switch-ota-bootstrap/main.c

@@ -0,0 +1,36 @@
+/*
+ * Tiny one-shot helper: swap a staged launcher NRO into place, then load the game.
+ * The main OTA launcher chainloads here because a running NRO cannot replace itself
+ * on sdmc/FAT.
+ */
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+#if defined(__SWITCH__)
+#include <switch.h>
+#endif
+
+#define INSTALL_DIR "sdmc:/switch/gen1recomp"
+#define STAGED INSTALL_DIR "/gen1recomp.nro.staged"
+#define LAUNCHER INSTALL_DIR "/gen1recomp.nro"
+#define GAME INSTALL_DIR "/gen1recomp-game.nro"
+
+int main(int argc, char **argv) {
+  (void)argc;
+  (void)argv;
+
+#if defined(__SWITCH__)
+  remove(LAUNCHER);
+  if (rename(STAGED, LAUNCHER) != 0) {
+    return 1;
+  }
+  Result rc = envSetNextLoad(GAME, GAME);
+  if (R_FAILED(rc)) return 1;
+  return 0;
+#else
+  fprintf(stderr, "ota-bootstrap: host stub (would rename %s -> %s, load %s)\n", STAGED, LAUNCHER,
+          GAME);
+  return 0;
+#endif
+}