Include Dynamic attribute in METADATA and PKG-INFO.

In all cases it should still be absent, but that may change as other dynamic attributes are supported.

whey/builder.py

@@ -402,6 +402,7 @@ def add_multiple(key: str, field: str) -> None:
 			for value in self.config[key]:
 				metadata_mapping[field] = str(value)  # pylint: disable=loop-invariant-statement
 
+		add_multiple("dynamic", "Dynamic")
 		metadata_mapping.update(self.parse_authors())
 
 		add_not_none("description", "Summary")
@@ -463,7 +464,7 @@ def write_metadata(self, metadata_file: PathPlus, metadata_mapping: MetadataMapp
 		:param metadata_file:
 		"""
 
-		metadata_file.write_text(metadata.dumps(metadata_mapping))
+		metadata_file.write_clean(metadata.dumps(metadata_mapping))
 		self.report_written(metadata_file)
 
 	def call_additional_hooks(self) -> None: