Get checked-in sdk version directly

Author: ntkme

.github/workflows/build.yml

@@ -44,8 +44,15 @@ jobs:
           python3 sdk/tools/generate_package_config.py
           python3 sdk/tools/generate_sdk_version_file.py
 
-          cd sdk
-          gclient getdep --var sdk_tag | tr : = | tee -a $GITHUB_OUTPUT
+
+          tee /tmp/version.dart <<'EOF'
+          import 'dart:io' show Platform;
+
+          void main() {
+            print('version=' + Platform.version.split(' ')[0]);
+          }
+          EOF
+          sdk/tools/sdks/dart-sdk/bin/dart run /tmp/version.dart | tee -a $GITHUB_OUTPUT
 
       - name: Patch Dart SDK 2.19
         if: startsWith(inputs.ref, '2.19.')