Add `pread/pwrite` support on `__MACH__` (MacOS) in addition to `__unix__`.
@@ -18,7 +18,7 @@ extern "C" {
#if defined(MRB_WITHOUT_IO_PREAD_PWRITE)
# undef MRB_WITH_IO_PREAD_PWRITE
#elif !defined(MRB_WITH_IO_PREAD_PWRITE)
-# if defined(__unix__)
+# if defined(__unix__) || defined(__MACH__)
# define MRB_WITH_IO_PREAD_PWRITE
# endif
#endif
