Fix dockerfile syntax for ARGs and LABELs

docker/Dockerfile

@@ -1,14 +1,16 @@
+ARG BASE_IMAGE="openjdk:17-jdk-slim"
+FROM ${BASE_IMAGE}
+
+ARG BASE_IMAGE
 ARG CREATED=""
 ARG SOURCE=""
 ARG VERSION=""
-ARG BASE_IMAGE="openjdk:17-jdk-slim"
-FROM ${BASE_IMAGE}
 
-LABEL org.opencontainers.image.authors="Eclipse Foundation"\
-      org.opencontainers.image.created=${CREATED}\
-      org.opencontainers.image.source="${SOURCE}"\
-      org.opencontainers.image.version="${VERSION}"\
-      org.opencontainers.image.base.name="${BASE_IMAGE}"
+LABEL org.opencontainers.image.authors="Eclipse Foundation"
+LABEL org.opencontainers.image.created="${CREATED}"
+LABEL org.opencontainers.image.source="${SOURCE}"
+LABEL org.opencontainers.image.version="${VERSION}"
+LABEL org.opencontainers.image.base.name="${BASE_IMAGE}"
 
 ### user name recognition at runtime w/ an arbitrary uid - for OpenShift deployments
 COPY uid_entrypoint /usr/local/bin/uid_entrypoint