twister: coverage: GCOVR as defautlt coverage reporting tool

Twister now uses GCOVR by default as the more reliable code
coverage reporting tool instead of LCOV.

(cherry picked from commit 8e3a3b4)

Original-Signed-off-by: Dmitrii Golovanov <dmitrii.golovanov@intel.com>
GitOrigin-RevId: 8e3a3b4
Change-Id: If4c9d10d8422dcfa43b24f13d571df7311669b75
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/zephyr/+/5149747
Tested-by: ChromeOS Prod (Robot) <chromeos-ci-prod@chromeos-bot.iam.gserviceaccount.com>
Commit-Queue: Fabio Baltieri <fabiobaltieri@google.com>
Reviewed-by: Fabio Baltieri <fabiobaltieri@google.com>
Tested-by: Fabio Baltieri <fabiobaltieri@google.com>

doc/develop/test/coverage.rst

@@ -142,7 +142,11 @@ or::
 
     $ twister --coverage -p native_sim -T tests/bluetooth
 
-which will produce ``twister-out/coverage/index.html`` with the report.
+which will produce ``twister-out/coverage/index.html`` report as well as
+the coverage data collected by ``gcovr`` tool in ``twister-out/coverage.json``.
+
+Other reports might be chosen with ``--coverage-tool`` and ``--coverage-formats``
+command line options.
 
 The process differs for unit tests, which are built with the host
 toolchain and require a different board::

scripts/pylib/twister/twisterlib/environment.py

@@ -305,7 +305,7 @@ def add_parse_arguments(parser = None):
                              "This option may be used multiple times. "
                              "Default to what was selected with --platform.")
 
-    parser.add_argument("--coverage-tool", choices=['lcov', 'gcovr'], default='lcov',
+    parser.add_argument("--coverage-tool", choices=['lcov', 'gcovr'], default='gcovr',
                         help="Tool to use to generate coverage report.")
 
     parser.add_argument("--coverage-formats", action="store", default=None, # default behavior is set in run_coverage