Fix issues with no-cache flag and new builder

Author: saville

buildrunner/docker/multiplatform_image_builder.py

@@ -323,7 +323,8 @@ def _build_single_image(
         build_kwargs = {}
         if builder:
             build_kwargs["builder"] = builder
-        if cache:
+        # Handle both no cache and cache
+        if cache is not None:
             build_kwargs["cache"] = cache
         if pull:
             build_kwargs["pull"] = pull