Do you use this PR for the autotools build? The first commit of this PR extends the autotools build a bit (for example 24x24 geany.png and LexillaLicense.txt)
My autotools build was with current GIT master from Geany directly. Just tried again from the meson branch and then the file differences are related to the `x86_64-linux-gnu` infix. So it's all fine, great!
gtk theme cache requires very recent meson, see previous discussion.
I'm using Meson from Debian Testing: 0.61.2
The libdir story is really messy, will have a look.
I don't mind the final path at all. If it's all in `lib/x86_64-linux-gnu` this is probably fine. I just think, G-P with Autotools should then also use the same path, otherwise Geany won't find the installed plugins.