David Tolnay a0f850f15b
Show error details during miri setup in CI
Without this, if it fails, the only information printed is useless:

    Preparing a sysroot for Miri (target: x86_64-unknown-linux-gnu)...
    fatal error: failed to build sysroot; run `cargo miri setup` to see the error details
2023-05-23 08:29:47 -07:00
..