[gardening] Ensure to fetch flutter repo tags before running flutter.

Lack of tags cause flutter get outdated version name, causing runtime errors like https://ci.chromium.org/ui/p/dart/builders/ci.sandbox/flutter-analyze/29634/infra

TEST=ci

Change-Id: Ibad39a5eb8f45aff9af22741b0c81c895e5ef4c0
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/450103
Reviewed-by: Devon Carew <[email protected]>
Commit-Queue: Alexander Aprelev <[email protected]>

Author: aam

tools/bots/flutter/analyze_flutter.sh

@@ -83,6 +83,9 @@ analyze_flutter_packages() {
 echo Cloning flutter/flutter...
 git clone --single-branch -vv \
   https://dart.googlesource.com/external/github.com/flutter/flutter
+pushd flutter
+git fetch --tags
+popd
 
 analyze_engine
 analyze_flutter_sdk

tools/bots/flutter/compile_flutter.sh

@@ -57,6 +57,7 @@ git clone --single-branch -vv \
     https://dart.googlesource.com/external/github.com/flutter/flutter
 
 pushd flutter
+git fetch --tags
 bin/flutter config --no-analytics
 bin/flutter update-packages
 pushd engine