When comparing meson and autotools installed files as instructed here, there is a diff them, but I think meson is correct and I'm not willing to fix autotools:
-./usr/lib/x86_64-pc-linux-gnu -./usr/lib/x86_64-pc-linux-gnu/xfce4 -./usr/lib/x86_64-pc-linux-gnu/xfce4/panel -./usr/lib/x86_64-pc-linux-gnu/xfce4/panel/plugins -./usr/lib/x86_64-pc-linux-gnu/xfce4/panel/plugins/libxfce4dict.so +./usr/lib/xfce4 +./usr/lib/xfce4/panel +./usr/lib/xfce4/panel/plugins +./usr/lib/xfce4/panel/plugins/libxfce4dict.so
