set analysis server exitCode on invalid cmdline arguments

pkg/analysis_server/lib/http_server.dart

Index: pkg/analysis_server/lib/http_server.dart
diff --git a/pkg/analysis_server/lib/http_server.dart b/pkg/analysis_server/lib/http_server.dart
index 3fb08de909499298307d253c6fa2008b797bfc87..c295e649e5f61bfb43aa397660eb9de76877d6b2 100644
--- a/pkg/analysis_server/lib/http_server.dart
+++ b/pkg/analysis_server/lib/http_server.dart
@@ -74,6 +74,7 @@ class HttpAnalysisServer {
       print('Missing required port number');
       print('');
       _printUsage(parser);
+      exitCode = 1;
       return;
     }
 
@@ -85,6 +86,7 @@ class HttpAnalysisServer {
       print('Invalid port number: ${results[PORT_OPTION]}');
       print('');
       _printUsage(parser);
+      exitCode = 1;
       return;
     }
   }