[sdks] Update checked-in SDKs to 3.7.0

Change-Id: Ib3be215f63e7e60deeec4c75e5bf3a2ceaac8116
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/409340
Commit-Queue: Martin Kustermann <[email protected]>
Reviewed-by: Martin Kustermann <[email protected]>
Auto-Submit: Alexander Thomas <[email protected]>

Author: athomas

DEPS

@@ -50,7 +50,7 @@ vars = {
   # Checked-in SDK version. The checked-in SDK is a Dart SDK distribution
   # in a cipd package used to run Dart scripts in the build and test
   # infrastructure, which is automatically built on the release commits.
-  "sdk_tag": "git_revision:f863f0b43625eb04539a34d7cc25029ba80dd522",
+  "sdk_tag": "git_revision:a8bfb132c5f7b9555d13ea79eaf0eaa77825824d",
 
   # co19 is a cipd package automatically generated for each co19 commit.
   # Use tests/co19/update.sh to update this hash.