Install binaries to the miri toolchain's sysroot The default install produces this behavior: ``` $ cargo +miri miri --version miri 0.1.0 (0ba1f4a0 2023-03-05) $ cargo +nightly miri --version miri 0.1.0 (0ba1f4a0 2023-03-05) ``` Which is not good. We've effectively erased the toolchain selection, and users may reasonably conclude that their rustup install is broken. After this change, we now get this: ``` $ cargo +miri miri --version miri 0.1.0 (0ba1f4a0 2023-03-05) $ cargo +nightly miri --version miri 0.1.0 (f63ccaf 2023-03-06) ``` Thanks `@jyn514` who all but wrote this for me.