Add Host filesystem mount to hook-docker:

This is helpful for Action images that might
need access to root Host filesystem locations.
For example, when using https://github.com/jaypipes/ghw
in an Action. ghw needs access to udev data that only
exists in the Host filesystem.

Signed-off-by: Jacob Weinstock <[email protected]>

Author: jacobweinstock

linuxkit-templates/hook.template.yaml

@@ -176,6 +176,7 @@ services:
       - /var/run/docker:/var/run
       - /var/run/images:/var/lib/docker
       - /var/run/worker:/worker
+      - /:/host_root
     runtime:
       mkdir:
         - /var/run/images