Fix bad sdk-path error message
Fix bad sdk-path error message

Fixes #48959

Change-Id: I2ebbb06583886a8e54dbda0a4222bc02d380f7fc
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/244742
Commit-Queue: Samuel Rawlins <5cf2cac5eec2ad6d0eb2b0f4ff6af9a590ce2bf6@google.com>
Reviewed-by: Brian Wilkerson <1f7641b6b14c52b9163524ab8d9aabff80176f21@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk