The dtrace build logic was copied straight out of the old Hotspot build
system, and is quite convoluted.
It should be split into the separate parts it actually contains of:
1) A gensrc step which runs with other gensrc ahead of compilation
2) Two independent libraries that can be build at any time
3) Two special dtrace-generated .o files that must be linked with the JVM
I have also cleaned up includes in generateJvmOffsets.cpp.
I have verified with COMPARE_BUILD that no changes has happened in any