Fix size of struct kinfo_file on 32-bit FreeBSD

https://github.com/freebsd/freebsd-src/blob/main/sys/sys/user.h

(backport <#3948>)
(cherry picked from commit f2b8b8f)

Author: asomers

src/unix/bsd/freebsdlike/freebsd/mod.rs

@@ -1645,7 +1645,7 @@ s_no_extra_traits! {
         pub kf_flags: ::c_int,
         _kf_pad0: ::c_int,
         pub kf_offset: i64,
-        _priv: [::uintptr_t; 38], // FIXME if needed
+        _priv: [u8; 304],   // FIXME: this is really a giant union
         pub kf_status: u16,
         _kf_pad1: u16,
         _kf_ispare0: ::c_int,