spring-build was previously included via an svn:external. Adding
directly to the source tree under Git to avoid the need for a git
submodule.
In order to build from any earlier commit, it is recommended to
export spring-build or symlink an existing copy into the root
of the spring-framework project and then build normally.
$ svn export https://src.springsource.org/svn/spring-build/tags/project-build-2.5.2 spring-build
