libsql-sqlite3: Sync ext/misc/fileio.c symlink fixes from 3.46.1

The 3.46.1 merge updated shell8.test (adding the symlink extraction
tests shell8-3.x) and the bundled MultipleCiphers fileio.c, but left
libsql-sqlite3/ext/misc/fileio.c at 3.44.0. That file is embedded into
the CLI shell via 'INCLUDE ../ext/misc/fileio.c', so '.ar -x' ran the
stale writeFile() and the new tests failed with
'failed to create symlink: link1'.

Bring writeFile() in line with upstream 3.46.1:

  - Skip utimes() on symbolic links. utimes() follows the link to its
    target; the archive only contains link1 -> file1 (no file1), so the
    dangling link made utimes() fail and broke the first extraction
    (shell8-3.2).
  - unlink(zFile) before symlink() so re-extraction does not fail with
    EEXIST (shell8-3.3).