bitbake: knotty: prevent extra logger from being enabled for tinfoil

tinfoil sets up its own logger by default, but if and when we initialise
the UI (by default knotty) will also set one up, leading to duplicated
messages specifically from tasks. To avoid this, rather than adding some
kind of parameter, just check if there is already a logger outputting to
stdout/stderr and if so, skip adding our own.

Part of the fix for [YOCTO #11275].

(Bitbake rev: 66d866745f35468d1540a793d07e3a401298b84b)

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/msg.py

@@ -216,3 +216,10 @@ def logger_create(name, output=sys.stderr, level=logging.INFO, preserve_handlers
         logger.handlers = [console]
     logger.setLevel(level)
     return logger
+
+def has_console_handler(logger):
+    for handler in logger.handlers:
+        if isinstance(handler, logging.StreamHandler):
+            if handler.stream in [sys.stderr, sys.stdout]:
+                return True
+    return False