On occasion it would be handy to customize a workspace or set of workspaces so that for just that workspace or set of workspaces it would use certain ALT* settings or override other makefile settings.

Having an optional j2se/make/common/shared/PrivateDefs.gmk file that would not be SCCS'd in (perhaps SCCS in a PrivateDefs.gmk-example) that would be used when it exists would work.

Probably should issue a WARNING message when this file is used so it's obvious.

In the Serviceability area it's common to be working on changes in a separate area that require a special or custom build of hotspot, and that workspace will only build with that custom version. This allows for easy setting of an ALT_HOTSPOT_IMPORT_PATH in that case.

I'm sure there are other uses for such a thing.

Default is to not have the file, which means NO impact to current builds.