lib/wasm: provide fs.constants.O_DIRECTORY definition
CL 606658 added a constants.Get("O_DIRECTORY").Int() call at init time,
which panics in browsers because O_DIRECTORY is undefined. It needs to
be a JavaScript number to avoid that.
Fixes #70723.
Change-Id: I727240bd25b47401d14a5e1a364d460708803f1f
Reviewed-on: https://go-review.googlesource.com/c/go/+/634455
TryBot-Bypass: Dmitri Shuralyov <dmitshur@golang.org>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org> Reviewed-by: Ian Lance Taylor <iant@google.com> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com> Reviewed-by: Zxilly Chou <zhouxinyu1001@gmail.com>