Add support for unlinked summary inputs through --build-summary-unlinked-input

pkg/analyzer_cli/lib/src/options.dart

Index: pkg/analyzer_cli/lib/src/options.dart
diff --git a/pkg/analyzer_cli/lib/src/options.dart b/pkg/analyzer_cli/lib/src/options.dart
index 338aceeef39ef92c50c737da50280113427c020e..485b3462ca191e9acda84604383fb36bdf31b975 100644
--- a/pkg/analyzer_cli/lib/src/options.dart
+++ b/pkg/analyzer_cli/lib/src/options.dart
@@ -52,6 +52,9 @@ class CommandLineOptions {
   /// List of summary file paths to use in build mode.
   final List<String> buildSummaryInputs;
 
+  /// List of unlinked summary file paths to use in build mode.
+  final List<String> buildSummaryUnlinkedInputs;
+
   /// Whether to skip analysis when creating summaries in build mode.
   final bool buildSummaryOnly;
 
@@ -161,6 +164,8 @@ class CommandLineOptions {
         buildMode = args['build-mode'],
         buildModePersistentWorker = args['persistent_worker'],
         buildSummaryInputs = args['build-summary-input'] as List<String>,
+        buildSummaryUnlinkedInputs =
+            args['build-summary-unlinked-input'] as List<String>,
         buildSummaryOnly = args['build-summary-only'],
         buildSummaryOnlyDiet = args['build-summary-only-diet'],
         buildSummaryOnlyUnlinked = args['build-summary-only-unlinked'],
@@ -280,7 +285,8 @@ class CommandLineOptions {
             'together with --build-summary-only.');
         return null; // Only reachable in testing.
       }
-      if (options.buildSummaryInputs.isNotEmpty) {
+      if (options.buildSummaryInputs.isNotEmpty ||
+          options.buildSummaryUnlinkedInputs.isNotEmpty) {
         printAndFail('No summaries should be provided in combination with '
             '--build-summary-only-unlinked, they aren\'t needed.');
         return null; // Only reachable in testing.
@@ -386,8 +392,13 @@ class CommandLineOptions {
           negatable: false,
           hide: hide)
       ..addOption('build-summary-input',
-          help: 'Path to a summary file that contains information from a '
-              'previous analysis run; may be specified multiple times.',
+          help: 'Path to a linked summary file that contains information from '
+              'a previous analysis run; may be specified multiple times.',
+          allowMultiple: true,
+          hide: hide)
+      ..addOption('build-summary-unlinked-input',
+          help: 'Path to an unlinked summary file that contains information '
+              'from a previous analysis run; may be specified multiple times.',
           allowMultiple: true,
           hide: hide)
       ..addOption('build-summary-output',