Fix a breakage introduced two commits ago

diff --git a/build.rb b/build.rb
index cae02e969b46421a15dd947048a6f7728125c6ef..7a1664784b009e3250713c2db4a1005c11d00893 100755 (executable)
--- a/build.rb
+++ b/build.rb
@@ -97,7 +97,7 @@ class Page
         s = a.join('/')
 
         @out_path = @site.output_dir + Pathname(s) + Pathname("index.html")
-        @url = "/#s/"
+        @url = "/#{s}/"
         @sort_url = @path.to_s.sub(/\.html$/, '')
     end