Fix native build docker multi-stage instructions

We need to ensure that maven can properly create its output

Fixes: #3114

docs/src/main/asciidoc/building-native-image-guide.adoc

@@ -285,6 +285,9 @@ In this guide we will use the first stage to generate the native executable usin
 FROM quay.io/quarkus/centos-quarkus-maven:{graalvm-version} AS build
 COPY src /usr/src/app/src
 COPY pom.xml /usr/src/app
+USER root
+RUN chown -R quarkus /usr/src/app
+USER quarkus
 RUN mvn -f /usr/src/app/pom.xml -Pnative clean package
 
 ## Stage 2 : create the docker final image