update gitignore for ISO images
update gitignore for ISO images

haiyang1992/NautilusVirtio,haiyang1992/NautilusVirtio,yhx189/nautilus,haiyang1992/NautilusVirtio,bradylee/nautilus_fs,yhx189/nautilus,bradylee/nautilus_fs,bradylee/nautilus_fs,yhx189/nautilus