Add include(GenerateExportHeader) to CMakeLists.txt

We should not depend on the fact that KDECompilerSettings.cmake happens
to include it when we use generate_export_header().

CMakeLists.txt

@@ -14,6 +14,7 @@ set(REQUIRED_QT_VERSION 5.2.0)
 find_package(Qt5Core ${REQUIRED_QT_VERSION} REQUIRED NO_MODULE)
 
 include(FeatureSummary)
+include(GenerateExportHeader)
 
 include(ECMSetupVersion)
 include(ECMGenerateHeaders)