Add ENv BUILD_OS to Dockerfiles

Author: shaun-nx

build/Dockerfile

@@ -17,6 +17,7 @@ COPY --from=ca-certs-provider --link /etc/ssl/certs/ca-certificates.crt /etc/ssl
 USER 101:1001
 ARG BUILD_AGENT
 ENV BUILD_AGENT=${BUILD_AGENT}
+ENV BUILD_OS=alpine
 ENTRYPOINT [ "/usr/bin/gateway" ]
 
 FROM common AS container

build/ubi/Dockerfile

@@ -17,6 +17,7 @@ COPY --from=ca-certs-provider --link /etc/ssl/certs/ca-certificates.crt /etc/ssl
 USER 101:1001
 ARG BUILD_AGENT
 ENV BUILD_AGENT=${BUILD_AGENT}
+ENV BUILD_OS=ubi
 
 LABEL name="F5 NGINX Gateway Fabric NGINX Plus" \
 	maintainer="[email protected]" \