compiler: Warn if --gir is used without --library
compiler: Warn if --gir is used without --library

https://bugzilla.gnome.org/show_bug.cgi?id=708693

frida/vala,frida/vala,frida/vala,GNOME/vala,frida/vala,GNOME/vala,GNOME/vala,frida/vala,GNOME/vala