build.gradle

// add this to the general build.gradle, not in the subproject's build.gradle
// improved version of Xavier's tip http://tools.android.com/tech-docs/new-build-system/tips#TOC-Improving-Build-Server-performance.

// usage example default, preDex will be enabled: gradle clean build
// usage example disabling preDex: gradle clean build -PpreDexEnable=false
// preDexEnable parameter's value can be set as property of Continuous Integration build config
// this is the main difference from Xavier's workaround where he doing only hasProperty check

project.ext {
    if (project.hasProperty('preDexEnable')) {
        project.ext.preDexLibs = project.properties['preDexEnable'].equals('true')
    } else {
        project.ext.preDexLibs = true // pre dexing should be true by default
    }

    println('PREDEX ' + (project.ext.preDexLibs ? 'ENABLED' : 'DISABLED')) // goes to build log or console output
}

subprojects {
    project.plugins.whenPluginAdded { plugin ->
        if ("com.android.build.gradle.AppPlugin".equals(plugin.class.name)) {
            project.android.dexOptions.preDexLibraries = rootProject.ext.preDexLibs
        } else if ("com.android.build.gradle.LibraryPlugin".equals(plugin.class.name)) {
            project.android.dexOptions.preDexLibraries = rootProject.ext.preDexLibs
        }
    }
}