title: Gradle fails with "Ambiguous method overloading for method java.io.File#<init>"
body: <p>When <code>gradle build</code>ing my project, I'm getting this error:</p>
  
  <blockquote>
    <p>FAILURE: Build failed with an exception.</p>
    
    <ul>
    <li><p>Where:<br> Build file 'App/build.gradle' line: 45</p></li>
    <li><p>What went wrong:<br> A problem occurred evaluating project ':App'.<br><strong>Ambiguous method overloading for method
    java.io.File#</strong>.<br>   Cannot resolve which method to invoke for
    [null, class java.lang.String] due to overlapping prototypes
    between:<br>      [class java.lang.String, class java.lang.String]<br>
    [class java.io.File, class java.lang.String]<br></p></li>
    </ul>
  </blockquote>
  
  <p>Said line is the first <code>proguardFile</code> rule:</p>
  
  <pre><code>buildTypes {
      release {
          debuggable false
          jniDebugBuild false
          signingConfig signingConfigs.(System.getenv("SIGNING_CONFIG") ?: "release")
          runProguard true
          proguardFile getDefaultProguardFile('proguard-android-optimize.txt')
          proguardFile 'proguard-rules.txt'
      }
  }
  </code></pre>
  
  <p>I haven't got any <code>local.properties</code> file, nor opened the project in Android Studio.</p>
  
  <p>What is wrong with my project? How can I fix this error?</p>