sysbuild: Add support for FILE_SUFFIX

Adds supports for sysbuild loading project-specific Kconfiguration
fragments that are suffixed with the user-provided value

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>

cmake/modules/configuration_files.cmake

@@ -90,9 +90,6 @@ DTC_OVERLAY_FILE=\"dts1.overlay dts2.overlay\"")
 # The DTC_OVERLAY_FILE variable is now set to its final value.
 zephyr_boilerplate_watch(DTC_OVERLAY_FILE)
 
-# Watch the FILE_SUFFIX variable for changes too
-zephyr_boilerplate_watch(FILE_SUFFIX)
-
 zephyr_get(EXTRA_CONF_FILE SYSBUILD LOCAL VAR EXTRA_CONF_FILE OVERLAY_CONFIG MERGE REVERSE)
 zephyr_get(EXTRA_DTC_OVERLAY_FILE SYSBUILD LOCAL MERGE REVERSE)
 zephyr_get(DTS_EXTRA_CPPFLAGS SYSBUILD LOCAL MERGE REVERSE)

share/sysbuild/cmake/modules/sysbuild_extensions.cmake

@@ -271,11 +271,9 @@ function(ExternalZephyrProject_Add)
     # Check for sysbuild related configuration fragments.
     # The contents of these are appended to the image existing configuration
     # when user is not specifying custom fragments.
-    if(NOT "${CONF_FILE_BUILD_TYPE}" STREQUAL "")
-      set(sysbuild_image_conf_fragment ${sysbuild_image_conf_dir}/${ZBUILD_APPLICATION}_${CONF_FILE_BUILD_TYPE}.conf)
-    else()
-      set(sysbuild_image_conf_fragment ${sysbuild_image_conf_dir}/${ZBUILD_APPLICATION}.conf)
-    endif()
+    zephyr_file(CONF_FILES ${sysbuild_image_conf_dir} KCONF sysbuild_image_conf_fragment
+                NAMES ${ZBUILD_APPLICATION}.conf SUFFIX ${FILE_SUFFIX}
+    )
 
     if (NOT (${ZBUILD_APPLICATION}_OVERLAY_CONFIG OR ${ZBUILD_APPLICATION}_EXTRA_CONF_FILE)
         AND EXISTS ${sysbuild_image_conf_fragment}