The main action here is to sink the creation of the installation rule for all of
the swift host tools into this API. In a latter commit, I will use this API to
create include and build rules for add_swift_host_tool.
Now that I am going to be adding an IN_SWIFT_COMPONENT argument, I need to do
this to distinguish the concepts of an LLVM_COMPONENT and a SWIFT_COMPONENT.
swift-reflection-test is now the test that forks a swift executable
and performs remote reflection, making it runnable on other targets,
such as the iOS simulator.
swift-reflection-dump is now a host-side tool that dumps the remote
reflection sections for any platform binary and will continue to
link in LLVM object file support.
This necessitates finally moving lib/Refleciton into stdlib/public,
since we're linking target-specific versions of the test tool and
we would eventually like to adopt some of this functionality in
the runtime anyway.
