enable multi-option contexts

See: #53876

With 0199e9d landed addressing #55413, this *should* now be safe to land.



Change-Id: I2c2a8d47ae0ede04f5de56b558f5e61778bf05f3
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/364020
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Phil Quitslund <pquitslund@google.com>

pkg/analyzer/lib/src/dart/analysis/context_locator.dart

@@ -31,7 +31,7 @@ class ContextLocatorImpl implements ContextLocator {
   /// analysis options file.
   ///
   /// See: https://github.com/dart-lang/sdk/issues/53876
-  static bool singleOptionContexts = true;
+  static bool singleOptionContexts = false;
 
   /// The resource provider used to access the file system.
   final ResourceProvider resourceProvider;