Correctly handle some consts declaration on macOS

Author: JohnTitor

src/unix/bsd/apple/mod.rs

@@ -4677,11 +4677,14 @@ cfg_if! {
             const __DARWIN_ALIGNBYTES32: usize = ::mem::size_of::<u32>() - 1;
             p + __DARWIN_ALIGNBYTES32 & !__DARWIN_ALIGNBYTES32
         }
-    } else if #[cfg(libc_const_size_of)] {
+    } else {
         fn __DARWIN_ALIGN32(p: usize) -> usize {
-            const __DARWIN_ALIGNBYTES32: usize = ::mem::size_of::<u32>() - 1;
+            let __DARWIN_ALIGNBYTES32: usize = ::mem::size_of::<u32>() - 1;
             p + __DARWIN_ALIGNBYTES32 & !__DARWIN_ALIGNBYTES32
         }
+    }
+
+    if #[cfg(libc_const_size_of)] {
         pub const THREAD_EXTENDED_POLICY_COUNT: mach_msg_type_number_t =
             (::mem::size_of::<thread_extended_policy_data_t>() / ::mem::size_of::<integer_t>())
             as mach_msg_type_number_t;