packaging icecat; compiles but build process deletes extensions

[ornx]

Hi all,

I am attempting to package GNU IceCat for NixOS, and the whole thing compiles 
and runs except that the Firefox build process deletes the GNUzilla extensions, 
so the resulting installation does not have any of the extensions it is 
supposed to come with. Having looked at the build error and source code a bit, 
I can see the script packager.py is calling copier.py, which is deleting them 
because they are not "registered". I don't understand why it is doing this, 
because all of the extensions are definitely present in the package-manifest.in 
file - does that script have some other conception of "registering" files?

Any advice would be appreciated. I have attached a log file which contains the 
last part of the failed build output.

icecaterror.txt
Description: Text document