add info on how to run an uberjar built with tools.build in the guide, …

…#561

content/guides/tools_build.adoc

@@ -140,18 +140,26 @@ When preparing an application, it is common to compile the full app + libs and a
                   :class-dir class-dir})
   (b/uber {:class-dir class-dir
            :uber-file uber-file
-           :basis basis}))
+           :basis basis
+           :main my.lib.main}))
 ----
 
 The deps.edn and build execution will look the same as the prior example.
 
 You can create the uber jar build with:
 
-[source,clojure]
+[source]
 ----
 clj -T:build uber
 ----
 
+The output of this build will be an uberjar at `target/lib1-1.2.100-standalone.jar`. That jar contains both a compiled version of this project and all of its dependencies. The uberjar will have a manifest referring to the `my.lib.main` namespaces (which should have a `-main` method) and can be invoked like this:
+
+[source]
+----
+java -jar target/lib1-1.2.100-standalone.jar
+----
+
 == Parameterized builds
 
 In the builds above we did not parameterize any aspect of the build, just chose which functions to call. You may find that it's useful to parameterize your builds to differentiate dev/qa/prod, or version, or some other factor. To account for function chaining at the command line, it is advisable to establish the common set of parameters to use across your build functions and have each function pass the parameters along.