Fix flutter build ipa --export-method not accepting enterprise flag (#153047)

When implementing the fix for flutter/flutter#149369, I missed accounting for the `enterprise` flag for `flutter build ipa` �

Fixes flutter/flutter#153000

Author: LouiseHsu

packages/flutter_tools/lib/src/commands/build_ios.dart

@@ -599,8 +599,6 @@ class BuildIOSArchiveCommand extends _BuildIOSSubCommand {
             return 'release-testing';
           case 'development':
             return 'debugging';
-          default:
-            throwToolExit('Encountered invalid export-method input.');
         }
       }
       return method;

packages/flutter_tools/test/commands.shard/hermetic/build_ipa_test.dart

@@ -554,6 +554,80 @@ void main() {
     XcodeProjectInterpreter: () => FakeXcodeProjectInterpreterWithBuildSettings(version: Version(15, 4, null)),
   });
 
+  testUsingContext('ipa build accepts "enterprise" export method when on Xcode versions <= 15.3', () async {
+    final BuildCommand command = BuildCommand(
+      artifacts: artifacts,
+      androidSdk: FakeAndroidSdk(),
+      buildSystem: TestBuildSystem.all(BuildResult(success: true)),
+      logger: logger,
+      fileSystem: fileSystem,
+      processUtils: processUtils,
+      osUtils: FakeOperatingSystemUtils(),
+    );
+    fakeProcessManager.addCommands(<FakeCommand>[
+      xattrCommand,
+      setUpFakeXcodeBuildHandler(),
+      exportArchiveCommand(exportOptionsPlist: _exportOptionsPlist),
+    ]);
+    createMinimalMockProjectFiles();
+    await createTestCommandRunner(command).run(
+        const <String>['build', 'ipa','--export-method', 'enterprise', '--no-pub']
+    );
+    expect(logger.statusText, contains('Building enterprise IPA'));
+  }, overrides: <Type, Generator>{
+    FileSystem: () => fileSystem,
+    Logger: () => logger,
+    ProcessManager: () => fakeProcessManager,
+    Platform: () => macosPlatform,
+    XcodeProjectInterpreter: () => FakeXcodeProjectInterpreterWithBuildSettings(version: Version(15, 3, null)),
+  });
+
+  testUsingContext('ipa build accepts "enterprise" export method when on Xcode versions > 15.3', () async {
+    final File cachedExportOptionsPlist = fileSystem.file('/CachedExportOptions.plist');
+    final BuildCommand command = BuildCommand(
+      artifacts: artifacts,
+      androidSdk: FakeAndroidSdk(),
+      buildSystem: TestBuildSystem.all(BuildResult(success: true)),
+      logger: logger,
+      fileSystem: fileSystem,
+      processUtils: processUtils,
+      osUtils: FakeOperatingSystemUtils(),
+    );
+    fakeProcessManager.addCommands(<FakeCommand>[
+      xattrCommand,
+      setUpFakeXcodeBuildHandler(),
+      exportArchiveCommand(exportOptionsPlist: _exportOptionsPlist, cachePlist: cachedExportOptionsPlist),
+    ]);
+    createMinimalMockProjectFiles();
+    await createTestCommandRunner(command).run(
+        const <String>['build', 'ipa','--export-method', 'enterprise', '--no-pub']
+    );
+
+    const String expectedIpaPlistContents = '''
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+    <dict>
+        <key>method</key>
+        <string>enterprise</string>
+        <key>uploadBitcode</key>
+        <false/>
+    </dict>
+</plist>
+''';
+
+    final String actualIpaPlistContents = fileSystem.file(cachedExportOptionsPlist).readAsStringSync();
+
+    expect(actualIpaPlistContents, expectedIpaPlistContents);
+    expect(logger.statusText, contains('Building enterprise IPA'));
+  }, overrides: <Type, Generator>{
+    FileSystem: () => fileSystem,
+    Logger: () => logger,
+    ProcessManager: () => fakeProcessManager,
+    Platform: () => macosPlatform,
+    XcodeProjectInterpreter: () => FakeXcodeProjectInterpreterWithBuildSettings(version: Version(15, 4, null)),
+  });
+
   testUsingContext('ipa build accepts legacy methods when on Xcode versions <= 15.3', () async {
     final BuildCommand command = BuildCommand(
       artifacts: artifacts,