In an Android app project, test project or library project built with Ant, the platform version to build against must be specified in either the project.properties or default.properties file, by setting the target parameter.
This build step will search for these files in your workspace, determine which target platform(s)
are required, and then ensure that they are installed. If the required platforms are already
installed, no action is taken.
Therefore it should always be safe to run this build step before any build steps which compile an
Android project.