[nrf fromtree] cmake: yaml: use APPEND PROPERTY to shorten code

Use a more concise way to append to a list property, as suggested in a
previous PR review.

Signed-off-by: Luca Burelli <[email protected]>
(cherry picked from commit 8e66848)

Author: pillo79

cmake/modules/yaml.cmake

@@ -476,9 +476,7 @@ function(yaml_save)
     set_property(TARGET ${save_target} PROPERTY json_file ${json_file})
 
     # comment this to keep the temporary JSON files
-    get_property(temp_files TARGET ${save_target} PROPERTY temp_files)
-    list(APPEND temp_files ${json_file})
-    set_property(TARGET ${save_target} PROPERTY temp_files ${temp_files})
+    set_property(TARGET ${save_target} APPEND PROPERTY temp_files ${json_file})
 
     FILE(GENERATE OUTPUT ${json_file}
       CONTENT "${json_content}"