Once we switch to using gold as linker, we can enable incremental linking where suitable. Libraries apart from hotspot is not considered at the moment, since link time is not so much of an issue except on hotspot.

Basically, we should *not* use incremental linking in the products we release. There is no big difference between incremental, and a fresh "full-incremental", but if we are not going to rebuild, we're wasting resources by using an incremental build.

All other builds, though, are candidates for incremental build. Two obvious candidates are all debug builds, but also all gtest libjvm builds (on both release and debug). If there is a developer request, we might also consider adding an option to build even the release libjvm.so using incremental linking.