[MRESOLVER-650] Fix demo for system properties

System properties were not added.

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https://issues.apache.org/jira/browse/MRESOLVER-650

Author: cstamas

maven-resolver-demos/maven-resolver-demo-snippets/src/main/java/org/apache/maven/resolver/examples/util/Booter.java

@@ -69,6 +69,7 @@ public static SessionBuilder newRepositorySystemSession(RepositorySystem system)
         FileSystem fs = Jimfs.newFileSystem(Configuration.unix());
         SessionBuilder result = new SessionBuilderSupplier(system)
                 .get()
+                .setSystemProperties(System.getProperties())
                 .withLocalRepositoryBaseDirectories(fs.getPath("local-repo"))
                 .setRepositoryListener(new ConsoleRepositoryListener())
                 .setTransferListener(new ConsoleTransferListener())