scp stalls on uploading in cygwin 3.5 current master.

[Takashi Yano]

Hi Corinna,

After the commit dedbbd74d0a8, "scp file server:." stalls.
I confirmed this when the "server" is a Linux machine.
The problem does not occur if it is reverted.

Could you please have a look?

commit dedbbd74d0a8f3b7dfae6188321703a47bb8a2b3
Author: Corinna Vinschen <corinna@vinschen.de>
Date:   Tue Aug 1 14:22:55 2023 +0200

    Cygwin: select: workaround FD_WRITE network event handling
    
    The FD_WRITE event is a false friend.  It indicates ready to write
    even if the next send fails with WSAEWOULDBLOCK.  *After* the fact,
    FD_WRITE will be cleared until sending is again possible, but that
    is too late for a select/write loop.
    
    Workaround that by using the WinSock select function when peeking
    at a socket and FD_WRITE gets indicated. WinSock select fortunately
    indicates writability correctly.
    
    Fixes: 70e476d27be8 ("(peek_socket): Use event handling for peeking socket.")
    Signed-off-by: Corinna Vinschen <corinna@vinschen.de>


-- 
Takashi Yano <takashi.yano@nifty.ne.jp>