fixed build for older qt versions

alethzero/CMakeLists.txt

@@ -63,7 +63,7 @@ target_link_libraries(${EXECUTABLE} Qt5::Core)
 target_link_libraries(${EXECUTABLE} Qt5::Widgets)
 target_link_libraries(${EXECUTABLE} Qt5::WebEngine)
 target_link_libraries(${EXECUTABLE} Qt5::WebEngineWidgets)
-if (APPLE)
+if (APPLE AND (NOT "${Qt5Core_VERSION_STRING}" VERSION_LESS "5.5"))
     target_link_libraries(${EXECUTABLE} Qt5::WebEngineCore)
 	target_link_libraries(${EXECUTABLE} Qt5::DBus)
 	target_link_libraries(${EXECUTABLE} Qt5::PrintSupport)

mix/CMakeLists.txt

@@ -21,7 +21,7 @@ if (("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang") AND NOT (CMAKE_CXX_COMPILER_VER
 endif ()
 
 find_package (Qt5WebEngine)
-if (APPLE)
+if (APPLE AND (NOT "${Qt5Core_VERSION_STRING}" VERSION_LESS "5.5"))
 # TODO: remove indirect dependencies once macdeployqt is fixed
 	find_package (Qt5WebEngineCore)
 	find_package (Qt5DBus)