GNOME Online Accounts is a single sign-on framework for GNOME. It aims 
to provide a way for users to setup online accounts to be used by the 
core system and core applications only. Calendar entries show up in 
GNOME Shell, e-mail in Evolution, online storages are exposed as 
GVolumes, and so on. 

Below variables are avaiable for configuration:
    GTKDOC=yes        : Build gtkdoc files
    INTROSPECTION=no  : Disable introspection for this build
    VALA=no           : Don't build Vala bindings