D18960: Add compile check to FindEGL

[Tobias C. Berner]

tcberner added a dependent revision: D19075: Fix FindEGL.

REPOSITORY
  R240 Extra CMake Modules

REVISION DETAIL
  https://phabricator.kde.org/D18960

To: hausmann, vkrause, apol
Cc: bcooksley, tcberner, kossebau, kde-frameworks-devel, kde-buildsystem, 
michaelh, ngraham, bruns