Set policy in examples

examples/CMakeLists.txt

@@ -22,6 +22,9 @@
 # M.Frank, CERN, 2015:  Adapt to new cmake scripts
 #==========================================================================
 cmake_minimum_required(VERSION 3.3 FATAL_ERROR)
+if (POLICY CMP0074)
+  cmake_policy(SET CMP0074 NEW) # CMake 3.12
+endif ()
 
 project( DD4hep_Examples )