fix symlink test on windows

Author: Qelxiros

library/std/src/sys/fs/windows.rs

@@ -1222,7 +1222,13 @@ impl Dir {
         unsafe {
             buffer.write(c::REPARSE_DATA_BUFFER {
                 ReparseTag: c::IO_REPARSE_TAG_SYMLINK,
-                ReparseDataLength: u16::try_from(size_of_val(&sym_buffer)).or(Err(TOO_LONG_ERR))?,
+                ReparseDataLength: u16::try_from(
+                    size_of::<c::REPARSE_DATA_BUFFER>()
+                        + size_of::<c::SYMBOLIC_LINK_REPARSE_BUFFER>()
+                        + usize::from(file_name_len) * 2
+                        - offset_of!(c::REPARSE_DATA_BUFFER, Reserved),
+                )
+                .or(Err(TOO_LONG_ERR))?,
                 Reserved: 0,
                 rest: (),
             });
@@ -1244,7 +1250,12 @@ impl Dir {
                 linkfile.handle.as_raw_handle(),
                 c::FSCTL_SET_REPARSE_POINT,
                 &raw const buffer as *const c_void,
-                u32::try_from(size_of_val(&buffer)).or(Err(TOO_LONG_ERR))?,
+                u32::try_from(
+                    size_of::<c::REPARSE_DATA_BUFFER>()
+                        + size_of::<c::SYMBOLIC_LINK_REPARSE_BUFFER>()
+                        + usize::from(file_name_len) * 2,
+                )
+                .or(Err(TOO_LONG_ERR))?,
                 ptr::null_mut(),
                 0,
                 ptr::null_mut(),