Ack use of wpkgwininfo var in openssh_srv.xml

This package is used only in Maths, and will need some refactoring
to be more widely applicable

tests/config.yml

@@ -16,6 +16,9 @@ package_glob: ../packages/*.xml
 #  - 7zip.xml
 #  - winscp.xml
 
+variable_names_to_skip:
+  openssh_srv.xml:
+    - wpkgwininfo
 
 # This should be a suitable subset of the default env vars
 # expected in the ucam_wpkg repo.