[BUG] Attachments not resolved correctly from symlinked Org files

[Karthik Chikmagalur <karthikchikmagalur@gmail.com>]

Attachment paths are not resolved correctly when the Org file is
symlinked elsewhere. This may or may not be a bug, but I think it's
undesired behavior:

1. Create an Org file somewhere, say ~/Desktop/test.org.

2. In test.org, create an attachment: `C-c C-a m' as a file.  Either the
   "copy" or "move" attachment method can be used.

3. Symlink test.org from elsewhere, say

/tmp/test.org -> ~/Desktop/test.org

4. In a fresh Emacs session, open /tmp/test.org and try to open the
attachment directory (`C-c C-a f').

Two things happen:

- An empty directory is created, like
  /tmp/data/48/2697ee-913c-4eee-b1fb-636416d3fb6b

- The original attachment can't be found, since it's actually in
  ~/Desktop/data/48/2697ee-913c-4eee-b1fb-636416d3fb6b

Tested with `emacs -q' with Org 9.6.23, and with commit
1ae978f940c0f88473f2232177c63a0de7fb7a1c from two weeks ago.

Karthik