Fix build_multiple_images threading default

Author: shanejbrown

buildrunner/docker/multiplatform_image_builder.py

@@ -403,7 +403,7 @@ def build_multiple_images(
         path: str = ".",
         file: str = "Dockerfile",
         target: Optional[str] = None,
-        use_threading: bool = False,
+        use_threading: bool = True,
         build_args: dict = None,
         inject: dict = None,
         cache: bool = False,