gitignore: Add new shim binary to gitignore list
gitignore: Add new shim binary to gitignore list

After new shim mocks have been added to the repository, we forgot to
add their binary names to the gitignore list.

Signed-off-by: Sebastien Boeuf <90b401417360b1924ef3f520ddee932686110f85@intel.com>

containers/virtcontainers,containers/virtcontainers