[nrf fromtree] samples: boards: nordic: coresight_stm: more logs from nrfutil

Make easier debugging nrfutil call.

Signed-off-by: Piotr Kosycarz <piotr.kosycarz@nordicsemi.no>
(cherry picked from commit de1d79b)

Author: nordic-piks

samples/boards/nordic/coresight_stm/pytest/test_stm.py

@@ -203,7 +203,12 @@ def nrfutil_dictionary_from_serial(
     try:
         # run nrfutil trace in background non-blocking
         logger.info(f"Executing:\n{cmd}")
-        proc = subprocess.Popen(cmd.split(), stdout=subprocess.DEVNULL)
+        proc = subprocess.Popen(cmd.split(),
+                                stdin=subprocess.PIPE,
+                                stdout=subprocess.PIPE,
+                                stderr=subprocess.STDOUT,
+                                encoding='UTF-8',
+                                errors='replace')
     except OSError as exc:
         logger.error(f"Unable to start nrfutil trace:\n{cmd}\n{exc}")
     try:
@@ -212,6 +217,8 @@ def nrfutil_dictionary_from_serial(
         pass
     finally:
         _kill(proc)
+        outs, errs = proc.communicate()
+        logger.info(f"{outs=}\n{errs=}")
 
 
 def test_sample_STM_decoded(dut: DeviceAdapter):