[ORC] Ensure that llvm_orc_registerJITLoaderGDBAllocAction is linked into tools.

Add a reference to llvm_orc_registerJITLoaderGDBAllocAction from the
linkComponents function in the lli, llvm-jitlink, and llvm-jitlink-executor
tools. This ensures that llvm_orc_registerJITLoaderGDBAllocAction is not
dead-stripped in optimized builds, which may cause failures in these tools.

The llvm_orc_registerJITLoaderGDBAllocAction function was originally added with
MachO debugging support in 69be352a, but that patch failed to update the
linkComponents functions.

http://llvm.org/PR56817