aedi: `BuildTarget.update_text_file()` restores modification time after write

the primary reason for this change is to avoid update of files at build step when these files were created at configuration step

aedi/target/base.py

@@ -131,9 +131,13 @@ class BuildTarget(Target):
         if content == patched_content:
             return
 
+        file_time = os.stat(path).st_mtime
+
         with open(path, 'w') as f:
             f.writelines(patched_content)
 
+        os.utime(path, (file_time, file_time))
+
     @staticmethod
     def _update_variables_file(path: Path, prefix_value: str,
                                processor: typing.Optional[typing.Callable] = None, quotes: bool = True):