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