pkg/host: add O_NONBLOCK to isSupportedOpenFile
pkg/host: add O_NONBLOCK to isSupportedOpenFile

Since commit 4f7e1d0f5e1c ("sys/linux: use openat for /dev/cdrom")
changed syz_open_dev to openat syzkaller tries to open /dev/cdrom
with r,w,rw flags. However, if there is no media in a cdrom
device these attempts will fail resulting in:
> disabling openat$sr: open(/dev/sr0) failed: no medium found

Add O_RDONLY|O_NONBLOCK mode to successfully open cdrom devices
with no media.

Signed-off-by: Denis Efremov <accabd4edc44e4dbbf4e6307bae515853f535251@linux.com>

xairy/syzkaller,xairy/syzkaller,google/syzkaller,xairy/syzkaller,xairy/syzkaller,google/syzkaller,google/syzkaller,google/syzkaller,google/syzkaller,xairy/syzkaller,google/syzkaller,google/syzkaller,xairy/syzkaller,xairy/syzkaller