In the AUR you can find the latest available version, it can be
downloaded and built using yaourt (or a similar AUR helper) using
yaourt -S remmina-plugin-exec
and then following the AUR helper instructions.
For anyone which doesn't want to use AUR the tar.xz package can be downloaded from the Download page and installed using:
cd "~/folder with the downloaded file"
sudo pacman -U "file name.pkg.tar.xz"
To build Remmina Plugin Exec from the source code you will need also Remmina Plugin Builder, a minimal development environment to build plugins for Remmina.
The building process simply needs the extraction of both Remmina Plugin Builder and Remmina Plugin Exec source code using:
cd "~/folder with the downloaded files"
tar xzf remmina-plugin-builder-*.tar.gz
tar xzf remmina-plugin-exec-*.tar.gz
Next you will need to compile the plugin using:
cp -r remmina-plugin-builder-*/* build
cp -r remmina-plugin-exec-*/* build/remmina-plugin-to-build
cmake -DCMAKE_INSTALL_PREFIX=/usr .
sudo make install
sudo gtk-update-icon-cache -q /usr/share/icons/hicolor/
After the installation, if no errors were reported the folder build can be removed and the same for the downloaded source package.
Warning! After executing the manual installation from source code an automatic software uninstall will not be possibile but you will have to manually delete all the installed files that were reported during the last installation step.