libkcal tests: small improvement to cmake code to avoid having to escape quotes.

Signed-off-by: Slávek Banko <slavek.banko@axis.cz>
Signed-off-by: Michele Calgaro <michele.calgaro@yahoo.it>

libkcal/tests/CMakeLists.txt

@@ -46,8 +46,8 @@ foreach( _test_name ${_test_executables} )
 	)
 endforeach( )
 
-set_target_properties( testfields
- PROPERTIES COMPILE_FLAGS -DINPUT='\"${CMAKE_CURRENT_SOURCE_DIR}/data/test_pilot.ics\"'
+set_property( TARGET testfields APPEND PROPERTY
+  COMPILE_DEFINITIONS INPUT="${CMAKE_CURRENT_SOURCE_DIR}/data/test_pilot.ics"
 )