Missing ia32-libs
Problem
:android_gingerbread_mr1:processReleaseResources FAILED FAILURE: Build failed with an exception. * What went wrong: Execution failed for task ':android_gingerbread_mr1:processReleaseResources'. > Could not call IncrementalTask.taskAction() on task ':android_gingerbread_mr1:processReleaseResources'
If you run gradle with --stacktrace you'll get the following:
Caused by: java.io.IOException: Cannot run program "/opt/android-studio/sdk/build-tools/18.1.1/aapt": error=2, No such file or directory
Solution
The android tools are 32 bit and if you're on 64 bit it will not be able to find them unless you have the 32 bit emulation layers. Did you do the following?
$ sudo apt-get install ia32-libs