Grails 2.3.0.M1 Maven Repo Credentials

BuildConfig.groovy

grails.servlet.version = "3.0" // Change depending on target container compliance (2.5 or 3.0)
grails.project.class.dir = "target/classes"
grails.project.test.class.dir = "target/test-classes"
grails.project.test.reports.dir = "target/test-reports"
grails.project.work.dir = "target/work"
grails.project.target.level = 1.6
grails.project.source.level = 1.6
//grails.project.war.file = "target/${appName}-${appVersion}.war"

forkConfig = [maxMemory: 1024, minMemory: 64, debug: false, maxPerm: 256]
grails.project.fork = [
   test: forkConfig, // configure settings for the test-app JVM
   run: forkConfig, // configure settings for the run-app JVM
   war: forkConfig, // configure settings for the run-war JVM
   console: forkConfig // configure settings for the Swing console JVM
]

grails.project.dependency.resolver = "maven" // or ivy
grails.project.dependency.resolution = {
    // inherit Grails' default dependencies
    inherits("global") {
        // specify dependency exclusions here; for example, uncomment this to disable ehcache:
        // excludes 'ehcache'
    }
    log "error" // log level of Ivy resolver, either 'error', 'warn', 'info', 'debug' or 'verbose'
    checksums true // Whether to verify checksums on resolve
    legacyResolve false // whether to do a secondary resolve on plugin installation, not advised and here for backwards compatibility

    repositories {
        inherits true // Whether to inherit repository definitions from plugins

        grailsPlugins()
        grailsHome()
        mavenLocal()
        grailsCentral()
        mavenCentral()
        mavenRepo("http://repo.mycustomrepo.com") {
          //Add authentication details to repository connection
          auth([
            username: 'myusername',
            password: 'myhiddenpassword'
          ])
        }
        // uncomment these (or add new ones) to enable remote dependency resolution from public Maven repositories
        //mavenRepo "http://repository.codehaus.org"
        //mavenRepo "http://download.java.net/maven/2/"
        //mavenRepo "http://repository.jboss.com/maven2/"
    }

    dependencies {
        // specify dependencies here under either 'build', 'compile', 'runtime', 'test' or 'provided' scopes e.g.
        // runtime 'mysql:mysql-connector-java:5.1.24'
    }

    plugins {
        // plugins for the build system only
        build ":tomcat:7.0.39"

        // plugins for the compile step
        compile ":scaffolding:1.0.0"
        compile ':cache:1.0.1'

        // plugins needed at runtime but not for compilation
        runtime ":hibernate:3.6.10.M3" // or ":hibernate4:4.1.11.BUILD-SNAPSHOT"
        runtime ":database-migration:1.3.3"
        runtime ":jquery:1.9.1"
        runtime ":resources:1.2"
        // Uncomment these (or add new ones) to enable additional resources capabilities
        //runtime ":zipped-resources:1.0.1"
        //runtime ":cached-resources:1.1"
        //runtime ":yui-minify-resources:0.1.5"
    }
}

Have you found a way to externalize these credentials to a file that's external to the project? Used to be able to do this via the ~/.grails/settings.groovy file, as shown here: http://jira.grails.org/browse/GRAILS-5316, but that no longer works.