/!\ Experimental code !
On your computer :
1- setup https-everywhere : https://www.eff.org/https-everywhere
2- change MY_HOSTNAME by your hostname in googleapis.xml
3- move googleapis.xml to $HOME/.mozilla/firefox/YOUR_PROFILE/HTTPSEverywhereUserRules/
On your server :
4- create the folder /mycdn
5- put index.php and .htaccess in /mycdn/
6- check that mod_rewrite is enabled
7- go on http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js
If it works, you will be redirected to your server.
You can go on https://MY_HOSTNAME/mycdn/list to see files in your cache.
If you have any bug, please report it.