[Orc] Refactor JITCompileCallbackManagerBase and CompileOnDemandLayer to support
target-independent callback management.

This is a prerequisite for adding orc-based lazy-jitting to lli.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@233166 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed