Fix BazelFileUriResolverTest on Windows.
Fix BazelFileUriResolverTest on Windows.

Change-Id: If1ffd02ad840af861e86dbeeaafb23805a225608
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/240140
Reviewed-by: Brian Wilkerson <1f7641b6b14c52b9163524ab8d9aabff80176f21@google.com>
Commit-Queue: Konstantin Shcheglov <09e4d7516628963212bf4aace2f97603d2b706e4@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