If the version is unchanged, don't write to the file. Ninja will notice the modification time is unchanged and avoid rebuilding the target's dependents.
In particular, this means merely adding or amending a commit will no longer make the VM and all SDK snapshots dirty.
Change-Id: I25617c6c584d1d1094a339fe14716d18b28c688f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/506101
Reviewed-by: Alexander Aprelev <aam@google.com>
Commit-Queue: Ryan Macnak <rmacnak@google.com>
Ryan Macnak
cf5494aa89