[nrf fromlist] tests: boot: Fix bootloader.mcuboot boot loop for nrf platforms

The swapped_app image, added via ExternalZephyrProject_Add,
wasn't receiving the swap method configuration from sysbuild.
If trying to build the test with a different configuration than
SWAP_USING_OFFSET (for example SWAP_USING_MOVE)
this resulted in a boot loop due to configuration mismatch
between swapped_image and mcuboot.

This fix ensures proper configuration propagation and prevents
similar mismatches in future scenarios.

Upstream PR #: 96921

Signed-off-by: Artur Hadasz <[email protected]>

Author: ahasztag

tests/boot/test_mcuboot/sysbuild.cmake

@@ -14,6 +14,12 @@ ExternalZephyrProject_Add(
   SOURCE_DIR ${APP_DIR}/swapped_app
 )
 
+# This section ensures that sysbuild-related configurations, such as the MCUBOOT swap type,
+# are passed down to the swapped_app image.
+set_target_properties(swapped_app PROPERTIES
+  IMAGE_CONF_SCRIPT ${ZEPHYR_BASE}/share/sysbuild/image_configurations/MAIN_image_default.cmake
+)
+
 # Add the swapped app to the list of images to flash
 # Ensure the flashing order of images is as follows:
 # - mcuboot