I noticed that geany-plugins localization files are missing in the macOS bundle. After some investigation I noticed this line:
https://github.com/geany/geany-plugins/blob/0bfe89d1a4da1d3781e7465e2ae2db9b...
It searches for the po files inside the `conf_dir` (which is different when doing out of tree build) but I think it should be `srcdir` like in Geany's case:
https://github.com/geany/geany/blob/75def8a24eb2dab8d376ae051806128827d34fbe...
Not sure if this change is enough or something else is needed. I'll leave the patch to someone else as me and autotools aren't friends ;-).