[flutter_tools] Deferred components setup validator (#75739)

packages/flutter_tools/lib/src/build_system/targets/common.dart

@@ -45,6 +45,10 @@ const String kExtraFrontEndOptions = 'ExtraFrontEndOptions';
 /// This is expected to be a comma separated list of strings.
 const String kExtraGenSnapshotOptions = 'ExtraGenSnapshotOptions';
 
+/// Whether the app should run gen_snapshot as a split aot build for deferred
+/// components.
+const String kSplitAot = 'SplitAot';
+
 /// Whether to strip source code information out of release builds and where to save it.
 const String kSplitDebugInfo = 'SplitDebugInfo';