Improve source for containerd/runc copy

This improves getting the source for the binaries that are compiled on
the system so that they can be copied into the bundles output.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

hack/make.sh

@@ -307,7 +307,7 @@ copy_containerd() {
         if [ -x /usr/local/bin/docker-runc ]; then
             echo "Copying nested executables into $dir"
 	    for file in containerd containerd-shim containerd-ctr runc; do
-                cp "/usr/local/bin/docker-$file" "$dir/"
+                cp `which "docker-$file"` "$dir/"
                 if [ "$2" == "hash" ]; then
                     hash_files "$dir/docker-$file"
 		fi