Do apt installs before running our scripts.

circle.yml

@@ -22,13 +22,13 @@ machine:
         echo 'python "${HOME}/${SCRIPT}.py" "$@"' >> "${HOME}/script.sh"
         chmod +x "${HOME}/script.sh"
   post:
+    - sudo apt-get update; sudo apt-get install xsltproc
     - exec "${HOME}/script.sh" machine_post
 checkout:
   post:
     - exec "${HOME}/script.sh" checkout_post
 dependencies:
   pre:
-    - sudo apt-get update; sudo apt-get install xsltproc
     - exec "${HOME}/script.sh" dependencies_pre
   override:
     - exec "${HOME}/script.sh" dependencies_override