[nrf fromlist] samples: boards: nordic: coresight_stm: Add RTT configuration

Add sample configuration that uses RTT backend for STM logging.

Upstream PR #: 100570

Signed-off-by: Krzysztof Chruściński <[email protected]>

Author: nordic-krch

samples/boards/nordic/coresight_stm/sample.yaml

@@ -41,6 +41,17 @@ tests:
       - SB_CONFIG_APP_CPUPPR_RUN=y
       - SB_CONFIG_APP_CPUFLPR_RUN=y
 
+  sample.boards.nrf.coresight_stm.rtt:
+    required_snippets:
+      - nordic-log-stm
+    extra_configs:
+      - CONFIG_DEBUG_NRF_ETR_BACKEND_RTT=y
+      - CONFIG_DEBUG_NRF_ETR_BACKEND_UART=n
+      - CONFIG_SEGGER_RTT_BUFFER_SIZE_UP=8192
+    extra_args:
+      - SB_CONFIG_APP_CPUPPR_RUN=y
+      - SB_CONFIG_APP_CPUFLPR_RUN=y
+
   sample.boards.nrf.coresight_stm.local_uart:
     harness: console
     harness_config: