configure: fixup Windows

Signed-off-by: Jens Axboe <axboe@kernel.dk>
configure: add default compiler on Windows

Signed-off-by: Jens Axboe <axboe@kernel.dk>
windows: don't provide strsep(), fio already has one

Signed-off-by: Jens Axboe <axboe@kernel.dk>