community/fwupd: handle no plugins installed
When no plugins are installed, the plugin directory is not available because all plugins are split of in subpackages. However, fwupd daemon will access this directory to load any installed plugins. It aborts when the directory does not exist. Therefore, create an empty directory during build to handle the case when the user hasn't installed any plugins. Also add a merged patch to avoid an assert when no plugins are installed. This patch can be dropped when the next fwupd release is available.
CC: @psykose (thanks for helping on IRC!)