gold-plugin: Implement parallel LTO code generation using llvm::splitCodeGen.

Parallelism can be enabled using a new plugin option, jobs=N, where N is
the number of code generation threads.

Differential Revision: http://reviews.llvm.org/D12308

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@246584 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed