feat(tfut): support unit testing build config

By adding support for the unit testing build config in the test
group, the CI will be able to build the unit tests based on that
config.

We are not targeting specific groups yet. There isn't anything
that checks whether it is of a specific group of tests and transforms
the config. This will be addressed in a further patch.

Signed-off-by: Juan Pablo Conde <juanpablo.conde@arm.com>
Signed-off-by: Edward Potapov <edward.potapov@arm.com>
Change-Id: I79f4a356c183d29d3758759fe1a54596c57fe536
diff --git a/script/gen_test_desc.py b/script/gen_test_desc.py
index 030e7c8..fa68ce1 100755
--- a/script/gen_test_desc.py
+++ b/script/gen_test_desc.py
@@ -60,9 +60,9 @@
     build_config, run_config = test.split(":")
 
     # Test descriptors are always generated in the following order:
-    #  tf_config, tftf_config, spm_config, rmm_config
+    #  tf_config, tftf_config, spm_config, rmm_config, tfut_config
     # Fill missing configs to the right with "nil".
-    config_list = (build_config.split(",") + ["nil"] * 4)[:4]
+    config_list = (build_config.split(",") + ["nil"] * 5)[:5]
 
     # Perform any group-specific translation on the config
     config_list = translate_build_config(group, config_list)