Update the verify_exported script to include the symbols for ICU data (#7647)

testing/symbols/pubspec.yaml

 name: verify_exported
 dependencies:
   path: 1.6.2
+  collection: 1.14.11

testing/symbols/verify_exported.dart

@@ -2,6 +2,7 @@ import 'dart:convert';
 import 'dart:io';
 
 import 'package:path/path.dart' as p;
+import 'package:collection/collection.dart' show MapEquality;
 
 // This script verifies that the release binaries only export the expected
 // symbols.
@@ -92,16 +93,19 @@ int _checkAndroid(String outPath, String nmPath, Iterable<String> builds) {
       continue;
     }
     final Iterable<NmEntry> entries = NmEntry.parse(nmResult.stdout);
-    if (entries.isEmpty) {
-      print('ERROR: $libFlutter exports no symbol');
-      print(' Expected exactly one symbol "JNI_OnLoad" of type "T", but got none.');
-      failures++;
-    } else if (entries.length > 1 || entries.first.type != 'T' || entries.first.name != 'JNI_OnLoad') {
-      print('ERROR: $libFlutter exports unexpected symbols.');
-      print('  Expected exactly one symbol "JNI_OnLoad" of type "T", but got instead:');
-      print(entries.fold<String>('', (String previous, NmEntry entry) {
-        return '${previous == '' ? '' : '$previous\n'}     ${entry.type} ${entry.name}';
-      }));
+    final Map<String, String> entryMap = Map.fromIterable(
+        entries,
+        key: (entry) => entry.name,
+        value: (entry) => entry.type);
+    final Map<String, String> expectedSymbols = {
+      'JNI_OnLoad': 'T',
+      '_binary_icudtl_dat_size': 'A',
+      '_binary_icudtl_dat_start': 'D',
+    };
+    if (!MapEquality<String, String>().equals(entryMap, expectedSymbols)) {
+      print('ERROR: $libFlutter exports the wrong symbols');
+      print(' Expected $expectedSymbols');
+      print(' Library has $entryMap.');
       failures++;
     } else {
       print('OK: $libFlutter');