When checking out the latest version from git, I get the error
Running intltoolize --automake --copy --force
cp: cannot create regular file ‘m4/intltool.m4’: No such file or directory
intltoolize: cannot copy '/usr/share/aclocal/intltool.m4' to 'm4/intltool.m4'
The file exists in /usr/share/aclocal, but the directory m4 does not.
This only occurs when freshly cloning the repository, hence it went unnoticed.
Fixed in http://git.xfce.org/panel-plugins/xfce4-cpufreq-plugin/commit/?id=eac601bc177bd252cd65715a6b5d30b51fd8f7fc.
Thanks for reporting.