component/fontconfig: strip path elements and don't include empty elements

This prevent some Fontconfig warnings ("empty font directory name ignored")
when the software includes empty items, which can easily happens with multi
level templates.

component/fontconfig/buildout.hash.cfg

 [template-fonts-conf]
 filename = fonts.conf.in
-md5sum = 6967e553630d107fc0a59b14de8b0251
+md5sum = a31030785c7b54bfd33320c87f6b5699

component/fontconfig/fonts.conf.in

@@ -14,10 +14,14 @@
  #}
 <fontconfig>
   <cachedir>{{ cachedir | escape}}</cachedir>
-  {% for font in fonts.splitlines() -%}
-    <dir>{{ font | escape}}</dir>
-  {% endfor %}
-  {% for include in includes.splitlines() -%}
-    <include>{{ include | escape}}</include>
-  {% endfor %}
+  {%- for font in fonts.splitlines() -%}
+    {% if font.strip() %}
+    <dir>{{ font.strip() | escape}}</dir>
+    {%- endif %}
+  {%- endfor %}
+  {%- for include in includes.splitlines() -%}
+    {% if include.strip() %}
+    <include>{{ include.strip() | escape}}</include>
+    {%- endif %}
+  {%- endfor %}
 </fontconfig>