Currently, the testsuite is the only thing depending on the `target has RTS linker` information provided by `ghc --info`. This information is based on a whitelist of supported architectures, and can be very simply implemented as a predicate in GHC in order to provide it in `ghc --info`. Contrary to this, we currently determine whether `target has RTS linker` or not in `configure`, and pass it around in hadrian and in the settings file unnecessarily. This came up in the refactor to support multiple toolchains. I'm pushing a clean up soon which makes this much simpler (and soft unblocks some of the multiple toolchain work).