rodei o seguinte comando: flutter build apk --flavor imm
e deu esse erro aqui:

Initializing gradle...                                              0,8s
Resolving dependencies...                                           5,1s
registerResGeneratingTask is deprecated, use registerGeneratedResFolders(FileCollection)
registerResGeneratingTask is deprecated, use registerGeneratedResFolders(FileCollection)
registerResGeneratingTask is deprecated, use registerGeneratedResFolders(FileCollection)
registerResGeneratingTask is deprecated, use registerGeneratedResFolders(FileCollection)
registerResGeneratingTask is deprecated, use registerGeneratedResFolders(FileCollection)
registerResGeneratingTask is deprecated, use registerGeneratedResFolders(FileCollection)
registerResGeneratingTask is deprecated, use registerGeneratedResFolders(FileCollection)
registerResGeneratingTask is deprecated, use registerGeneratedResFolders(FileCollection)
registerResGeneratingTask is deprecated, use registerGeneratedResFolders(FileCollection)
registerResGeneratingTask is deprecated, use registerGeneratedResFolders(FileCollection)
registerResGeneratingTask is deprecated, use registerGeneratedResFolders(FileCollection)
registerResGeneratingTask is deprecated, use registerGeneratedResFolders(FileCollection)
registerResGeneratingTask is deprecated, use registerGeneratedResFolders(FileCollection)
registerResGeneratingTask is deprecated, use registerGeneratedResFolders(FileCollection)
registerResGeneratingTask is deprecated, use registerGeneratedResFolders(FileCollection)
Running Gradle task 'assembleImmRelease'...
Note: C:\flutter\.pub-cache\hosted\pub.dartlang.org\connectivity-0.4.3+7\android\src\main\java\io\flutter\plugins\connectivity\ConnectivityPlugin.java uses or overrides a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
Note: C:\flutter\.pub-cache\hosted\pub.dartlang.org\firebase_auth-0.6.6\android\src\main\java\io\flutter\plugins\firebaseauth\FirebaseAuthPlugin.java uses or overrides a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
Note: C:\flutter\.pub-cache\hosted\pub.dartlang.org\firebase_auth-0.6.6\android\src\main\java\io\flutter\plugins\firebaseauth\FirebaseAuthPlugin.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
Note: C:\flutter\.pub-cache\hosted\pub.dartlang.org\firebase_core-0.2.5+1\android\src\main\java\io\flutter\plugins\firebase\core\FirebaseCorePlugin.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
Note: C:\flutter\.pub-cache\hosted\pub.dartlang.org\firebase_messaging-2.2.0+1\android\src\main\java\io\flutter\plugins\firebasemessaging\FlutterFirebaseInstanceIDService.java uses or overrides a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
Note: C:\flutter\.pub-cache\hosted\pub.dartlang.org\video_player-0.9.0\android\src\main\java\io\flutter\plugins\videoplayer\VideoPlayerPlugin.java uses or overrides a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
Calling mockable JAR artifact transform to create file: C:\Users\marcelo.reis\.gradle\caches\transforms-2\files-2.1\f0abf2831e22b8618e334f7705f5cded\android.jar with input C:\Users\marcelo.reis\AppData\Local\Android\sdk\platforms\android-28\android.jar
Calling mockable JAR artifact transform to create file: C:\Users\marcelo.reis\.gradle\caches\transforms-2\files-2.1\fa2a3208904b0b770b7c7ceb66a6044d\android.jar with input C:\Users\marcelo.reis\AppData\Local\Android\sdk\platforms\android-27\android.jar
Running Gradle task 'assembleImmRelease'...
Running Gradle task 'assembleImmRelease'... Done                  247,2s (!)
Gradle task assembleImmRelease failed with exit code 1