[ParallelCG] Add a new splitCodeGen() API which takes a TargetMachineFactory.

This is a recommit of r266390 with a fix that will allow tests to pass
(hopefully). Before we got a StringRef to M->getTargetTriple() and right
after we moved the Module so we were referencing a dangling object.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266456 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed