Use AnalysisOptions.signature as a way to check compatibility.

pkg/analysis_server/lib/src/status/get_handler.dart

Index: pkg/analysis_server/lib/src/status/get_handler.dart
diff --git a/pkg/analysis_server/lib/src/status/get_handler.dart b/pkg/analysis_server/lib/src/status/get_handler.dart
index d6ed6eb611db9cb741c4771156daa6f3eee62515..17d62291a6073bf6cfce5e8935eeded7408d0fae 100644
--- a/pkg/analysis_server/lib/src/status/get_handler.dart
+++ b/pkg/analysis_server/lib/src/status/get_handler.dart
@@ -421,7 +421,7 @@ class GetHandler implements AbstractGetHandler {
    */
   String _encodeSdkDescriptor(SdkDescription descriptor) {
     StringBuffer buffer = new StringBuffer();
-    buffer.write(descriptor.options.encodeCrossContextOptions().join(','));
+    buffer.write(descriptor.options.signature.join(','));
     for (String path in descriptor.paths) {
       buffer.write('+');
       buffer.write(path);