message: make sure that find_sysroot always sets MIRI_SYSROOT
diff: @@ -55,7 +55,6 @@ build_sysroot() {
  cargo run $CARGO_BUILD_FLAGS --bin cargo-miri -- miri setup "$@"
  # Call again, to just set env var.
  eval $(cargo run $CARGO_BUILD_FLAGS -q --bin cargo-miri -- miri setup --env "$@")
  - export MIRI_SYSROOT
  }
  # Prepare and set MIRI_SYSROOT. Respects `MIRI_TEST_TARGET` and takes into account
  @@ -73,7 +72,7 @@ find_sysroot() {
  build_sysroot --target "$MIRI_TEST_TARGET"
  else
  # Assume we have a proper host libstd in $SYSROOT.
  - true
  + MIRI_SYSROOT="$SYSROOT"
  fi
  else
  # A normal toolchain. We have to build a sysroot either way.
  @@ -83,6 +82,7 @@ find_sysroot() {
  build_sysroot
  fi
  fi
  + export MIRI_SYSROOT
  }
  ## Main
  