fix stat64 issue for modern macos versions (including macos arm64)

--- a/tools/rpcgen/rpc_main.c
+++ b/tools/rpcgen/rpc_main.c
@@ -68,6 +68,12 @@
 # endif
 #endif
 
+#ifdef __APPLE__
+# if __DARWIN_ONLY_64_BIT_INO_T
+#  define stat64 stat
+# endif
+#endif
+
 struct commandline
   {
     int cflag;			/* xdr C routines */