Flutter crash report; please file at https://github.com/flutter/flutter/issues.

## command

flutter --suppress-analytics build flx --target=lib/main.dart --output-file=/Users/ntrlab/semyon/apps/checker/ios/Flutter/app.flx --snapshot=build/snapshot_blob.bin --depfile=build/snapshot_blob.bin.d --working-dir=build/flx

## exception

FileSystemException: FileSystemException: Deletion failed, path = 'build/flx' (OS Error: Directory not empty, errno = 66)

```
#0      _Directory._deleteSync (dart:io/directory_impl.dart:162)
#1      FileSystemEntity.deleteSync (dart:io/file_system_entity.dart:411)
#2      ForwardingFileSystemEntity.deleteSync (package:file/src/forwarding/forwarding_file_system_entity.dart:68)
#3      _ZipToolBuilder.createZip (package:flutter_tools/src/zip.dart:69)
<asynchronous suspension>
#4      assemble (package:flutter_tools/src/flx.dart:142)
<asynchronous suspension>
#5      build (package:flutter_tools/src/flx.dart:79)
<asynchronous suspension>
#6      BuildFlxCommand.runCommand (package:flutter_tools/src/commands/build_flx.dart:44)
<asynchronous suspension>
#7      FlutterCommand.verifyThenRunCommand (package:flutter_tools/src/runner/flutter_command.dart:253)
<asynchronous suspension>
#8      FlutterCommand.run (package:flutter_tools/src/runner/flutter_command.dart:193)
<asynchronous suspension>
#9      CommandRunner.runCommand (package:args/command_runner.dart:194)
<asynchronous suspension>
#10     FlutterCommandRunner.runCommand (package:flutter_tools/src/runner/flutter_command_runner.dart:279)
<asynchronous suspension>
#11     CommandRunner.run.<anonymous closure> (package:args/command_runner.dart:109)
#12     new Future.sync (dart:async/future.dart:222)
#13     CommandRunner.run (package:args/command_runner.dart:109)
#14     FlutterCommandRunner.run (package:flutter_tools/src/runner/flutter_command_runner.dart:162)
#15     run.<anonymous closure> (package:flutter_tools/executable.dart:143)
<asynchronous suspension>
#16     AppContext._run (package:flutter_tools/src/base/context.dart:76)
<asynchronous suspension>
#17     AppContext.runInZone.<anonymous closure> (package:flutter_tools/src/base/context.dart:66)
#18     _rootRun (dart:async/zone.dart:1120)
#19     _CustomZone.run (dart:async/zone.dart:1001)
#20     runZoned (dart:async/zone.dart:1467)
#21     AppContext.runInZone (package:flutter_tools/src/base/context.dart:65)
#22     run (package:flutter_tools/executable.dart:114)
<asynchronous suspension>
#23     main (package:flutter_tools/executable.dart:67)
<asynchronous suspension>
#24     main (file:///Users/ntrlab/semyon/flutter/packages/flutter_tools/bin/flutter_tools.dart:16)
#25     _startIsolate.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:263)
#26     _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:151)
```

## flutter doctor

```
[✓] Flutter (on Mac OS X 10.12.6 16G29, locale en-RU, channel alpha)
    • Flutter at /Users/ntrlab/flutter
    • Framework revision 4424892c79 (2 weeks ago), 2017-10-10 16:45:11 -0700
    • Engine revision 2a84f18c79
    • Tools Dart version 1.25.0-dev.11.0

[✓] Android toolchain - develop for Android devices (Android SDK 26.0.2)
    • Android SDK at /Users/ntrlab/Library/Android/sdk
    • Platform android-26, build-tools 26.0.2
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_112-release-b06)

[✓] iOS toolchain - develop for iOS devices (Xcode 9.0)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 9.0, Build version 9A235
    • ios-deploy 1.9.2
    • CocoaPods version 1.2.1

[✓] Android Studio (version 2.3)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Java version OpenJDK Runtime Environment (build 1.8.0_112-release-b06)

[✓] IntelliJ IDEA Community Edition (version 2017.2.5)
    • Flutter plugin version 18.1
    • Dart plugin version 172.4155.35

[✓] Connected devices
    • iPhone 6 • 2CED9AE2-FCDE-4D77-ABEA-728E320A28C5 • ios • iOS 11.0 (simulator)

```