[gen_snapshot] Escape paths when writing loading unit manifests.
[gen_snapshot] Escape paths when writing loading unit manifests.

Bug: https://github.com/dart-lang/sdk/issues/41974
Change-Id: I030629110026bbc4b1c339764ed805f65f753448
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/154827
Reviewed-by: Alexander Markov <239e774fd29abc1267878f57afe1a8a03e0ca887@google.com>
Commit-Queue: Ryan Macnak <d738b7f001baf9789095d7dc549cff6de60b011d@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