[Android][Resolved] Error:Execution failed for task ':app:mergeDebugResources'. > Executor Singleton not started

To start the executor singleton , you need to updated your root projects build.gradle file to use latest gradle version (suggested by EBLiS in stackoverflow).

Method 1 : 

Step1

Change Android Plugin for Gradle Version By Android User interface
Select menu File > Project Structure > Project.

Step2

Visit Android office site of Android Plugin for Gradle Release Notes and check for the latest Android Plugin for Gradle version.
http://developer.android.com/tools/revisions/gradle-plugin.html

and right now (29/02/2016) the latest Android Plugin for Gradle version is 1.5.0 (November 2015), be ware the requirement before using the latest version.

latest version Android Plugin for Gradle, Revision 1.5.0 requires
  a) Gradle 2.2.1 or higher
  b) Build Tools 21.1.1 or higher

Step3

Let check is the project using (a) "Gradle 2.2.1 or higher" first, Select menu File > Project Structure > Project. And check value of field "Gradle version:", it's equal to the requirement "Gradle 2.2.1" and it pass.

Step4

And then check next one, "Build Tools 21.1.1 or higher", click your Android Application name ("in this case it's "app") "modules" in right panel, and then check the "Build Tools Version" in Properties tag. It's 21.1.2 and fit latest version Android Plugin for Gradle, Revision 1.5.0 requirement.

Step5

if you checked your project fit the requirements of the latest version Android Plugin for Gradle, you can use the latest version, otherwise you should use the earlier version. Way to change android Plugin version is Edit the text in red circle next to number 2. For example 1.5.0.

Method 2 : 

OR you can edit the root projects build.gradle file to change the gradle version directly.

Reference:

http://developer.android.com/tools/revisions/gradle-plugin.html
http://stackoverflow.com/questions/30315693/errorexecution-failed-for-task-libcompilereleaseaidl-executor-singleton