c285841a4f
This should make both static and dynamic NewPM plugins work with LTO. And as a bonus, it makes static linking of OldPM plugins more reliable for plugins with both an OldPM and NewPM interface. I only implemented the command-line flag to specify NewPM plugins in llvm-lto2, to show it works. Support can be added for other tools later. Differential Revision: https://reviews.llvm.org/D76866