Remove the old build system

The new build system ("build-infra") has been the default way of building the JDK for almost a year. Keeping the old build system in sync with the new requires time and effort, and is getting harder all the time.

So the time has come to finally kill of the old build system for those components where the new build system exists (i.e. langtools, jdk, corba, jaxp and jaxws -- but not hotspot).

The last internal user of the old build system just recently switched to the new build system, so we can finally pull this off.