after feedback from @meskio, probably the best way to do this is to run the nsis installer in two separate steps: build first the uninstaller, sign it, and then add it as a payload to the 2nd run.
i'm adding this to the installer scripts, and it's slightly convoluted, because you need to have wine installed (when you define a flag, you get a installer.exe that you then need to execute to produce the uninstaller). I was tempted to add wine 32bits to the docker image, but I think growing it 600Mb is too much.
I'd rather go the route of doing the 2-stages but doing the wine step in the host machine.
I also think I'd leave a flag for producing a non-signed uninstaller for the CI.
latest commits on !94 (closed) implement 2 stages inside the docker image, plus signing of the uninstaller and the installer (a one-step still need to be added so that the CI can produce a bundle).