When installing plugin files are installed to
/usr/local/lib64/xfce4/panel-plugins/ when all of my other plugins correctly
installed to /usr/lib64/xfce4/panel-plugins/.
Reproducible: Didn't try
Steps to Reproduce:
1. make application
2. install application
Files were installed in /usr/local/lib64/panel-plugins/ by default.
Install files into /usr/lib64/xfce4/panel-plugins/ by default.
Gentoo AMD64 install
That's what the --prefix option to configure is for. /usr/local is usually the
default for source installs in most packages.