gnu: Correct struct stat64 for sparc

Struct stat and stat64 needs to match when gnu_file_offset_bits64 is
set.

(backport <rust-lang#4345>)
(cherry picked from commit 22ac02c)

Author: snogge

src/unix/linux_like/linux/gnu/b32/sparc/mod.rs

@@ -102,7 +102,8 @@ s! {
         pub st_mtime_nsec: c_long,
         pub st_ctime: crate::time_t,
         pub st_ctime_nsec: c_long,
-        __reserved: [c_long; 2],
+        __glibc_reserved4: c_ulong,
+        __glibc_reserved5: c_ulong,
     }
 
     pub struct statfs64 {