This adds an explicit version of the SwiftRemoteMirror library for use
in the tools that comprise the toolchain. This is a separate build from
the target specific builds of the library even though we may be building
the runtime for the (same) host.
If one thinks about it, swift's build has two sections: a runtime or target
section (i.e. ./stdlib) and a host section (everything
else). swift-reflection-test is an abberation from that pattern since it is
built for target platforms but is in the section of host tools.
In this commit, I move it into ./stdlib. Beyond being a bitter location
conceptually this will additionally allow me to avoid a dependency cycle in
between the compiler and the stdlib build.
After this, there is only one more target in the compiler code: swift-lang. From
talking with Xi Ge, we can move that into its own separate project as a
package. Once that is done, I will not have any more cycles.
