jar file installed is read only

Hi,

I've created a Firebird extension and a xpi. I made it possible to 
install it as a user (on linux).

My problem is that the .jar file installed in the user's profile chrome 
  directory is read only. That prevents the user to upgrade (unless he 
changes user rights on the jar file). I use xulkit to generate the 
package, and the jar in the work directory is read-write.

I didn't find any reference to a way to define which permissions should 
be set on the installed file.

Thanks.

Raph