build: Ensure EGL related variables are defined even when EGL_CHECKED=yes
build: Ensure EGL related variables are defined even when EGL_CHECKED=yes

When checking for EGL earlier in the configure script (ie EGL_CHECKED is
"yes"), we did not execute some EGL code. Let's split that code in two:
  - A first part that has a last change to check for EGL
  - A second one that defines variables and that should always been run
    in an EGL build

Distrotech/cogl,gcampax/cogl,djdeath/cogl-android,djdeath/cogl-android,djdeath/cogl,spatulasnout/cogl,collects/cogl,collects/cogl,spatulasnout/cogl,djdeath/cogl,gcampax/cogl,gcampax/cogl,djdeath/cogl-android,Distrotech/cogl,Distrotech/cogl,gcampax/cogl,djdeath/cogl,Distrotech/cogl