feat(tofs): lookup files directory in “tpldir” hierarchy

Without user configuration, the “libtofs.jinja” lookup the “files”
directory under “tplroot” with is the base directory of the current
formula unless the “v1_path_prefix” is set.

Now, we lookup the directory in each sub-directory from the
sub-directory of the current SLS (“tpldir”) to the top level directory
of the formula (“tplroot”).

This permit to support formula with different components, each one
providing its own “files” directory like “systemd-formula”.

template/libtofs.jinja

@@ -66,8 +66,15 @@
   {%- set path_prefix_exts = [''] %}
   {%- if v1_path_prefix != '' %}
     {%- do path_prefix_exts.append(v1_path_prefix) %}
+  {%- elif tplroot != tpldir %}
+    {#- Walk directory tree to find {{ files_dir }} #}
+    {%- set subpath_parts = tpldir.lstrip(tplroot).lstrip('/').split('/') %}
+    {%- for path in subpath_parts %}
+      {%- set subpath = subpath_parts[0:loop.index] | join('/') %}
+      {%- do path_prefix_exts.append('/' ~ subpath) %}
+    {%- endfor %}
   {%- endif %}
-  {%- for path_prefix_ext in path_prefix_exts %}
+  {%- for path_prefix_ext in path_prefix_exts|reverse %}
     {%- set path_prefix_inc_ext = path_prefix ~ path_prefix_ext %}
     {#- For older TOFS implementation, use `files_switch` from the config #}
     {#- Use the default, new method otherwise #}