Fix missing task vars

pipelines/jobs/rust-xwin.yml.j2

@@ -25,7 +25,7 @@
               vars:
                 context: images/rust-xwin
                 target: rust-xwin
-                additional_targets: rust-xwin-ci
+                dockerfile: ''
               output_mapping:
                 image: image-rust-xwin
             - task: build-rust-xwin-ci
@@ -33,6 +33,7 @@
               vars:
                 context: images/rust-xwin
                 target: rust-xwin-ci
+                dockerfile: ''
               output_mapping:
                 image: image-rust-xwin-ci
       - in_parallel:

pipelines/jobs/simple-image.yml.j2

@@ -8,6 +8,8 @@
         file: repo/tasks/build-image.yml
         vars:
           context: images/{{ job.name }}
+          dockerfile: ''
+          target: ''
         {%- if "args" in job %}
         params:
         {%- for name, value in job.args.items() %}