[build] Copy cogl-enum-types.h under the guard
[build] Copy cogl-enum-types.h under the guard

We avoid rebuilding cogl-enum-types.h and cogl-enum-types.c by
using a "guard" -- a stamp file that will block Makefile. Since
we need cogl-enum-types.h into /clutter/cogl as well for the
cogl.h include to work, if we copy the cogl-enum-types.h
unconditionally it will cause a rebuild of the whole COGL; which
will cause a full rebuild.

To solve this, we can copy the header file when generating it
under the stamp file.

tardyp/clutter,jigpu/clutter,tardyp/clutter,djdeath/clutter,kerrickstaley/clutter-vala,jigpu/clutter,Distrotech/clutter,Distrotech/clutter,spatulasnout/clutter,GNOME/clutter,djdeath/clutter,djdeath/clutter-multithreaded,spatulasnout/clutter,nobled/clutter,spatulasnout/clutter,Distrotech/clutter,djdeath/clutter,rkudiyarov/clutter_osx,spatulasnout/clutter,jigpu/clutter,kerrickstaley/clutter-vala,djdeath/clutter-multithreaded,djdeath/clutter-android,kerrickstaley/clutter-vala,djdeath/clutter,GNOME/clutter,heysion/clutter-clone,dlespiau/clutter,collects/clutter,GNOME/clutter,collects/clutter,djdeath/clutter-multithreaded,Distrotech/clutter,djdeath/clutter-multithreaded,Distrotech/clutter,dlespiau/clutter,rkudiyarov/clutter_osx,tardyp/clutter,nobled/clutter,heysion/clutter-clone,heysion/clutter-clone,rkudiyarov/clutter_osx,djdeath/clutter,nobled/clutter,jigpu/clutter,GNOME/clutter,ebassi/clutter,collects/clutter,rkudiyarov/clutter_osx,ebassi/clutter,jigpu/clutter,ebassi/clutter,collects/clutter,heysion/clutter-clone,djdeath/clutter,djdeath/clutter-android,dlespiau/clutter,djdeath/clutter-android,heysion/clutter-clone,collects/clutter,Distrotech/clutter,djdeath/clutter-android,kerrickstaley/clutter-vala,spatulasnout/clutter,djdeath/clutter-android,GNOME/clutter,ebassi/clutter,jigpu/clutter,ebassi/clutter