[dart2wasm] Fix paths for snapshot.
[dart2wasm] Fix paths for snapshot.

Change-Id: I6b26b6171b35d22cdb706d96fdb0045eef7e7264
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/264100
Commit-Queue: Alexander Thomas <29642742b6693024c89de8232f2e2542cf7eedf7@google.com>
Auto-Submit: Joshua Litt <9f8daed1ab51574c9a48ffacb03e4a1adb4f880c@google.com>
Reviewed-by: Alexander Thomas <29642742b6693024c89de8232f2e2542cf7eedf7@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