package/zisofs-tools: new package

package/zisofs-tools: new package

To support transparent (de)compression in iso9660, we need mkzftree,
which comes from zisofs_tools, biundled with cdrkit.

However, cdrkit is a cmake package, but zisofs_tools is an autotools
package, so we need a separate package just to get mkzftree, but it is
pretty lightweight.

We just need the host variant for now,so we just add that.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
[Thomas: add entry to DEVELOPERS file, rename to zisofs-tools.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>