title: set android:value with a gradle properties on manifest
body: <p>I have my facebook application id on my gradle properties with : </p>
  
  <pre><code>FACEBOOK_APPLICATION_ID="XXXXXXXXXXXXXXX"
  </code></pre>
  
  <p>and I set in my defaultConfig : </p>
  
  <pre><code>manifestPlaceholders = [facebookAppId: FACEBOOK_APPLICATION_ID]
  </code></pre>
  
  <p>then, I want to use this in my manifest with : </p>
  
  <pre><code>&lt;meta-data
          android:name="com.facebook.sdk.ApplicationId"
          android:value="${facebookAppId}" /&gt;
  </code></pre>
  
  <p>but it doesn't work. The only things working are to set my faceboook id in a string : </p>
  
  <pre><code>&lt;meta-data
          android:name="com.facebook.sdk.ApplicationId"
          android:value="@string/facebook_app_id" /&gt;
  </code></pre>
  
  <p>or to put this directly with : </p>
  
  <pre><code>&lt;meta-data
          android:name="com.facebook.sdk.ApplicationId"
          android:value="\ XXXXXXXXXXXXXX" /&gt;
  </code></pre>
  
  <p>but I must set my facebook id in my gradle properties. What is the right way to do this ?</p>
  
  <p>Thanks.</p>