The Makefile default build target includes bin/synocli, but the
Dockerfile builder stage never copies synocli/ into the build context,
so building the image fails with
"stat /go/src/synok8scsiplugin/synocli: directory not found".
Copy synocli/ so the in-image make behaves the same as in a full
checkout.
The tool executor is capable of running given tools in chroot either by automatically locating the tools in path using the `env` command or directly if the path is known.
This removes the need for the shell script to wrap commands and reduces number of needed external binaries on the node.