Fix definition of FIODGNAME on 32-bit FreeBSD

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

(backport <rust-lang#3948>)
(cherry picked from commit 0b6cab8)

Author: asomers

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

@@ -3218,7 +3218,14 @@ cfg_if! {
     }
 }
 
-pub const FIODGNAME: ::c_ulong = 0x80106678;
+cfg_if! {
+    if #[cfg(target_pointer_width = "64")] {
+        pub const FIODGNAME: ::c_ulong = 0x80106678;
+    } else {
+        pub const FIODGNAME: ::c_ulong = 0x80086678;
+    }
+}
+
 pub const FIONWRITE: ::c_ulong = 0x40046677;
 pub const FIONSPACE: ::c_ulong = 0x40046676;
 pub const FIOSEEKDATA: ::c_ulong = 0xc0086661;