Add abiFilters to gradle properties

Following works with Gradle 2.3:

abiFilters 'x86', 'x86_64', 'armeabi', 'armeabi-v7a', 'arm64-v8a'

In gradle.properties you can have for example:

ABI_FILTERS=armeabi-v7a;x86 //delimiter can be anything (change below)

Then in build.gradle there is (for example in debug buildType section):

ndk {
  abiFilters = []
  abiFilters.addAll(ABI_FILTERS.split(';').collect{it as String})
}

Now each developer can choose independetly abi for his current testing device (gradle.properties is in .gitignore).

Thanks Igor Ganapolsky for starting hint.