gen_kobject_list.py: OrderedDict for < 3.6 determinism

Dictionaries are iterated in a random order by Python 3.5 and before.
This could have caused "Unstable" CI in PR #13921 and maybe others.
Anyway we want builds to be determimistic by default. Explicit
randomness can be added for better coverage but not by default.

1. When running "make kobj_types_h_target" repeatedly one can observe
that the following .h files keep changing in
build/zephyr/include/generated/:

- kobj-types-enum.h
- otype-to-str.h
- otype-to-size.h

Switching kobjects to OrderedDict makes these 3 .h files deterministic.

2. When running this test repeatedly with CONFIG_USERSPACE=y:

  rm build/zephyr/*.gperf && make -C build obj_list

... the dict used for --gperf-output seems to be deterministic, probably
because its keys are all integers (memory addresses). However we can't
take that for granted with Python < 3.6 so out of caution also switch
the output of find_objects() in elf_helper.py to a sorted OrderedDict.

PS: I would normally prefer official Python documentation to
StackOverflow however this one is a good summary and has all the
multiple pointers to the... official Python documentation.

Signed-off-by: Marc Herbert <marc.herbert@intel.com>

scripts/gen_priv_stacks.py

@@ -105,6 +105,9 @@ def main():
     syms = eh.get_symbols()
     max_threads = syms["CONFIG_MAX_THREAD_BYTES"] * 8
     objs = eh.find_kobjects(syms)
+    if not objs:
+        sys.stderr.write("WARNING: zero kobject found in %s\n"
+                         % args.kernel)
 
     thread_counter = eh.get_thread_counter()
     if thread_counter > max_threads: