Fix protobuf to build when pthreads is missing.

Change-Id: I36ae748e4c6ffc99ace23519c8d588426c684cce
Bring in VTK crosscompilation fix.

Change-Id: Id03ccca6d63f86e55fd6f2fd5f44a9935ed9fab5
Merge topic 'crosscompilation_fixes' into next

0bf00a4 Bring in VTK crosscompilation fix.
ad06090 Fix protobuf to build when pthreads is missing.