Allow for absolute path to inifile in dune_add_system_test

I have a meta-ini file that I configure with CMake's configure_file to set some paths before calling dune_add_system_test. I want to put the configured file into the build tree, but the path of the meta-ini file is hard-coded to be relative to ${CMAKE_CURRENT_SOURCE_DIR} in dune_add_system_test:

execute_process(COMMAND ${CMAKE_BINARY_DIR}/dune-env dune_has_static_section.py --ini ${CMAKE_CURRENT_SOURCE_DIR}/${SYSTEMTEST_INIFILE} RESULT_VARIABLE res)

Would be great if you could allow for an absolute path in this function, so I can do

dune_add_system_test(TARGET dorie INIFILE ${CMAKE_CURRENT_BINARY_DIR}/test.mini SCRIPT test_dorie.py)