cmake: trigger olddefconfig on kconfig changes

When there are changes made to Kconfig files it's better
to run olddefconfig automatically to prevent undesired behaviour,
like for example depending on added config that has some default value
that is not present because developer didn't run olddefconfig
after pulling changes.

Signed-off-by: Janusz Jankowski <janusz.jankowski@linux.intel.com>

scripts/cmake/kconfig.cmake

@@ -31,6 +31,26 @@ add_custom_target(
 	USES_TERMINAL
 )
 
+file(GLOB_RECURSE KCONFIG_FILES "${SOF_ROOT_SOURCE_DIRECTORY}/Kconfig")
+
+if(EXISTS ${DOT_CONFIG_PATH})
+	# Update with olddefconfig only if config was previously generated
+	add_custom_command(
+		OUTPUT ${DOT_CONFIG_PATH}
+		COMMAND ${CMAKE_COMMAND} -E env
+			srctree=${PROJECT_SOURCE_DIR}
+			CC_VERSION_TEXT=${CC_VERSION_TEXT}
+			ARCH=${ARCH}
+			${PYTHON3} ${PROJECT_SOURCE_DIR}/scripts/kconfig/olddefconfig.py
+			${PROJECT_SOURCE_DIR}/Kconfig
+		DEPENDS ${KCONFIG_FILES}
+		WORKING_DIRECTORY ${GENERATED_DIRECTORY}
+		COMMENT "Regenerating .config with olddefconfig"
+		VERBATIM
+		USES_TERMINAL
+	)
+endif()
+
 add_custom_command(
 	OUTPUT ${CONFIG_H_PATH}
 	COMMAND ${CMAKE_COMMAND} -E env