Fixed using libunwind on iOS, where it's only available on the simulator (thanks Vit!)
diff --git a/include/SDL_config_iphoneos.h b/include/SDL_config_iphoneos.h
index 38dcd9a..83b2734 100644
--- a/include/SDL_config_iphoneos.h
+++ b/include/SDL_config_iphoneos.h
@@ -44,7 +44,8 @@
#define HAVE_STDIO_H 1
#define HAVE_STRING_H 1
#define HAVE_SYS_TYPES_H 1
-#define HAVE_LIBUNWIND_H 1
+/* The libunwind functions are only available on x86 */
+/* #undef HAVE_LIBUNWIND_H */
/* C library functions */
#define HAVE_MALLOC 1