gplugin/gplugin

Remove join_paths from Meson files as much as possible.
develop
2020-02-29, Elliott Sales de Andrade
0685dd2a8a48
Remove join_paths from Meson files as much as possible.

With 0.50.0, we can use / directly.
The following individuals have contributed to this project.
Ankit Vani <a@nevitus.org>
EionRobb <eion@robbmob.com>
Elliott Sales de Andrade <quantum.analyst@gmail.com>
Gary Kramlich <grim@reaperworld.com>
Jason Scherer <schereja@gmail.com>
John Bailey <rekkanoryo@rekkanoryo.org>
Mike Ruprecht <cmaiku@gmail.com>
Olaf Hering <olaf@aepfle.de>
Richard Laager <rlaager@pidgin.im>