title: Configured Resources Per Flavor and BuildType Overwrites Each Other
body: <p>I have several flavors for which I'd like to configure specific resources for on a per buildType basis. </p>
  
  <p>The following configuration works perfectly if there's only one flavor, android recognizes the resource directories src/flavor1/res and src/flavor1/::buildType::/res as expected:</p>
  
  <pre><code>productFlavors {
      flavor1 {
          applicationId "com.flavor1"
          sourceSets {
              debug {
                  res.srcDirs = [ 'src/flavor1/debug/res' ]
              }
              staging {
                  res.srcDirs = [ 'src/flavor1/staging/res' ]
              }
              release {
                  res.srcDirs = [ 'src/flavor1/release/res' ]
              }
          }
      }
  }
  </code></pre>
  
  <p>However, if I add more than one flavor, the resource directory for the last flavor defined is the only one recognized regardless of what variant is currently selected in Android Studio:</p>
  
  <pre><code>productFlavors {
      flavor1 {
          applicationId "com.flavor1"
          sourceSets {
              debug {
                  res.srcDirs = [ 'src/flavor1/debug/res' ]
              }
              staging {
                  res.srcDirs = [ 'src/flavor1/staging/res' ]
              }
              release {
                  res.srcDirs = [ 'src/flavor1/release/res' ]
              }
          }
      }
      flavor2 {
          applicationId "com.flavor2"
          sourceSets {
              debug {
                  res.srcDirs = [ 'src/flavor2/debug/res' ]
              }
              staging {
                  res.srcDirs = [ 'src/flavor2/staging/res' ]
              }
              release {
                  res.srcDirs = [ 'src/flavor2/release/res' ]
              }
          }
      }
  }
  </code></pre>
  
  <p>In the above configuration, when I select flavor1Debug, for example, the following directories are recognized as the resource directories:</p>
  
  <pre><code>src/flavor1/res
  src/flavor2/debug/res
  </code></pre>
  
  <p>What am I missing?</p>