>Try checking if the "task" flag is set for "do_patch"
Good idea, thanks! It's working correctly. I can see both 'noexec' and
'task' flags can be set separately, so to make it more general (and make it
work for similar recipes without sources) I will check both 'noexec' and
'task' flags.
I will submit another patchset with suggested change  (see below) and with
another condition check to not affect kernel build.:

diff --git a/scripts/lib/devtool/standard.py
b/scripts/lib/devtool/standard.py
index 8b80fb8bfa..6f4cbbe219 100644
--- a/scripts/lib/devtool/standard.py
+++ b/scripts/lib/devtool/standard.py

-                if 'noexec' in (d.getVarFlags(task, False) or []):
+                if 'noexec' in (d.getVarFlags(task, False) or []) or
'task' not in (d.getVarFlags(task, False) or []):
...
-        if 'noexec' in (d.getVarFlags('do_patch', False) or []):
+        if not is_kernel_yocto and ('noexec' in (d.getVarFlags('do_patch',
False) or []) or 'task' not in (d.getVarFlags('do_patch', False) or []):

Best regards,
Tomasz Dziendzielski