New comment by Veganizer on void-packages repository

https://github.com/void-linux/void-packages/issues/25508#issuecomment-821168042

Comment:
XPCOM belongs to the Firefox Runtime xulrunner
https://github.com/duanyao/xulrunner-stub/blob/master/src/stub/nsXPCOMPrivate.h

It is outdated since firefox 41
https://github.com/zotero/translation-server-old/issues/24

Seems to be updated:
https://github.com/zotero/translation-server-old/pull/34
So you need Firefox SDK at least. Maybe you can package it?

I have found following pages too:
https://extensionworkshop.com/documentation/develop/comparison-with-xul-xpcom-extensions/
https://extensionworkshop.com/documentation/develop/porting-a-legacy-firefox-extension/