build: Fix the private pkg-config requirements
build: Fix the private pkg-config requirements

Private pkg-config requirements are conditional.

Distrotech/clutter,heysion/clutter-clone,collects/clutter,kerrickstaley/clutter-vala,heysion/clutter-clone,djdeath/clutter-multithreaded,ebassi/clutter,djdeath/clutter-multithreaded,djdeath/clutter-android,GNOME/clutter,jigpu/clutter,collects/clutter,djdeath/clutter-multithreaded,djdeath/clutter,collects/clutter,Distrotech/clutter,Distrotech/clutter,djdeath/clutter,ebassi/clutter,GNOME/clutter,djdeath/clutter-multithreaded,collects/clutter,GNOME/clutter,heysion/clutter-clone,djdeath/clutter-android,djdeath/clutter,jigpu/clutter,Distrotech/clutter,djdeath/clutter,djdeath/clutter-android,djdeath/clutter,kerrickstaley/clutter-vala,jigpu/clutter,djdeath/clutter,Distrotech/clutter,jigpu/clutter,ebassi/clutter,djdeath/clutter-android,ebassi/clutter,ebassi/clutter,Distrotech/clutter,GNOME/clutter,kerrickstaley/clutter-vala,djdeath/clutter-android,heysion/clutter-clone,jigpu/clutter,collects/clutter,heysion/clutter-clone,kerrickstaley/clutter-vala,GNOME/clutter,jigpu/clutter