Fix struct stat fields for darwin (#473)

Darwin doesn't support POSIX compatible stat fields when -fmodule

core/iwasm/libraries/libc-wasi/sandboxed-system-primitives/src/ssp_config.h

@@ -86,9 +86,9 @@
 #endif
 
 #ifdef __APPLE__
-#define st_atimespec st_atim
-#define st_mtimespec st_mtim
-#define st_ctimespec st_ctim
+#define st_atim st_atimespec
+#define st_ctim st_ctimespec
+#define st_mtim st_mtimespec
 #endif
 
 #ifdef __APPLE__