The original way of building static libraries in the JDK was to use the configure argument --enable-static-build, which set the value of the make variable STATIC_BUILD. (Note that this is not the same as the source code definition STATIC_BUILD, which will be set by other means as well.)

This method only ever worked on macOS, and has long since stopped working. It was originally introduced for the Mobile Project, but I've now learn that not even they use it anymore.

It just adds clutter to the build system, and should be removed.