The generator should handle this.
Let's see whether this works.

This is inspired by
flathub/com.irccloud.desktop@8e764be

Let's see how well this works.

The commit 394786b910a1d2ee35455210d923a360a425f03d of f-b-t says, that
electron/get >= 1.12.4 has a new behaviour. But we don't have such a new
version. Well, let's give this a try, anyway.

This reverts commit 120f7c9.

python3 ~/vcs/flatpak-builder-tools/node/flatpak-node-generator.py npm
~/vcs/deltachat-desktop/package-lock.json --recursive -s --output
generated-sources-npm.json

This reverts commit 22755ff.

I hope this tells us something why it thinks it hasn't already
downloaded the files.

This will hopefully make npm find the populated cache.

Forgive me, I have no idea, what I'm doing.

It seems that the Electron update is not necessary. At least the npm
install step seems to succeed.

This seems to be required in order for build4production to run.

This tries to find out why it can't find the zip files it's looking for.
Because they sort of exist!

Interestingly, it looks for both ../chromedriver-v10.0.0-linux-x64.zip
and ../electron-v11.1.0-linux-x64.zip.