Fix Jenkins oldev build

Jenkins rebuilds the oldev image when pip dependencies change, so
it needs to be able to set the nexus URL for package repos in the
build.

docker/Dockerfile.oldev

@@ -1,4 +1,10 @@
 FROM openlibrary/olbase:latest
+
+# Allow for nexus overrides
+ARG PIP_INDEX_URL
+ARG NPM_CONFIG_REGISTRY
+ARG HTTPS_PROXY
+
 WORKDIR /openlibrary
 
 COPY --chown=openlibrary:openlibrary requirements*.txt ./