fix missing deps in firefox plugin
fix missing deps in firefox plugin

this seems to be a copy and paste error, those common files should be copied
to the build directory and from there into the browser-specific directories.

Manouchehri/mailvelope,power12317/mailvelope,power12317/mailvelope,mommel/mailvelope,linagora/mailvelope,anthonymiyoro/mailvelope,anthonymiyoro/mailvelope,mommel/mailvelope,mommel/mailvelope,linagora/mailvelope,mailvelope/mailvelope,anthonymiyoro/mailvelope,linagora/mailvelope,Manouchehri/mailvelope,Manouchehri/mailvelope,mailvelope/mailvelope,mailvelope/mailvelope