OutputSubDir: Two sets of codes were generated

I set the outputSubDir for java:
```
protobuf {
//generatedFilesBaseDir = "$protoPath"
protoc {
// Download from repositories
artifact = "com.google.protobuf:protoc:3.15.6"
//generatedFilesBaseDir = "$protoPath"
}

plugins {
}

generateProtoTasks {
ofSourceSet('test').each { task ->
task.plugins {
java {
outputSubDir = "proto222"
}
}
}
}
}
```
Then run task `generateTestProto`, and it generates **two same cpoys**. Here is the result: