[nrf fromlist] cmake: dts: Use temporary file for dts.cmake

Uses a temporary file for dts output then uses CMake to copy to the
correct file if it has changed. This prevents a ping-pong issue when
sysbuild is used of configuring and building cycle when nothing has
changed and there is sysbuild code which loads in the devicetree
data from an image

Upstream PR #: 81340

Signed-off-by: Jamie McCrae <[email protected]>

Author: nordicjm

cmake/modules/dts.cmake

@@ -321,17 +321,26 @@ endif()
 #
 # Run GEN_DTS_CMAKE_SCRIPT.
 #
+# A temporary file is used copied to the original file if it differs, this prevents issue such as
+# a cycle when sysbuild is used of configuring and building multiple times due to the dts.cmake
+# file of images having a newer modification time than the sysbuild build.ninja file, despite the
+# output having not changed
+#
+set(dts_cmake_tmp ${DTS_CMAKE}.new)
 
 execute_process(
   COMMAND ${PYTHON_EXECUTABLE} ${GEN_DTS_CMAKE_SCRIPT}
   --edt-pickle ${EDT_PICKLE}
-  --cmake-out ${DTS_CMAKE}
+  --cmake-out ${dts_cmake_tmp}
   WORKING_DIRECTORY ${PROJECT_BINARY_DIR}
   RESULT_VARIABLE ret
   )
 if(NOT "${ret}" STREQUAL "0")
   message(FATAL_ERROR "gen_dts_cmake.py failed with return code: ${ret}")
 else()
+  zephyr_file_copy(${dts_cmake_tmp} ${DTS_CMAKE} ONLY_IF_DIFFERENT)
+  file(REMOVE ${dts_cmake_tmp})
+  set(dts_cmake_tmp)
   message(STATUS "Including generated dts.cmake file: ${DTS_CMAKE}")
   include(${DTS_CMAKE})
 endif()