When unlink fails, it is not yet known if the argument is a directory or not.
Since CL 588495, we figure out if it's a directory when trying to open
it (and, for a directory, return the original unlink error).
The (very minor) issue is, in case of a symlink, a different error is
returned -- usually it's ELOOP, but some systems use other values. Let's
account for that error code, too.
This is a followup to CL 588495.
Change-Id: I4ee10fe9b57f045fbca02f13e5c9ea16972803bc
Reviewed-on: https://go-review.googlesource.com/c/go/+/589376 Reviewed-by: Michael Pratt <mpratt@google.com>
Run-TryBot: Kirill Kolyshkin <kolyshkin@gmail.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@google.com>