adb: fix windows build after "forward --list" fix.

EWOULDBLOCK is not there on windows.
It gets translated by the adb_write() wrapper into EGAIN.
But the Linux one does not translate EWOULDBLOCK into EGAIN.
Without EWOULDBLOCK, it works just fine.

Change-Id: Ic293be392aa4364637428ea94ef87890ffa09b9b
Signed-off-by: JP Abgrall <jpa@google.com>