Fix bug in compilation step

UTests/CMakeLists.txt

@@ -19,6 +19,8 @@ file(
 # Adding the project sources dir as an include dir
 INCLUDE_DIRECTORIES(
      ${CMAKE_BINARY_DIR}/Src 
+     ${CMAKE_SOURCE_DIR}/Src   
+     ${SCALFMM_INCLUDES}
 )
 
 # Add execs - 1 cpp = 1 exec