Define PRIVATE on apple to expose OFD commands

Author: anacrolix

libc-test/build.rs

@@ -179,6 +179,7 @@ fn test_apple(target: &str) {
     let mut cfg = ctest_cfg();
     cfg.flag("-Wno-deprecated-declarations");
     cfg.define("__APPLE_USE_RFC_3542", None);
+    cfg.define("PRIVATE", None);
 
     headers! { cfg:
         "aio.h",