[MCJIT] Add command-line argument to llvm-rtdyld to specify target addresses for
sections.

This allows fine-grained control of the memory layout of hypothetical target
processes for testing purposes.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217122 91177308-0d34-0410-b5e6-96231b3b80d8