...
apply plugin: 'maven-publish'
...

publishing {
    repositories {
        maven {
            url "s3://BUCKET_NAME/release"
            credentials(AwsCredentials) {
                accessKey "AWS_ACCESS_KEY"
                secretKey "AWS_SECRET_KEY"
            }
        }
    }

    publications {
        mavenJava(MavenPublication) {
            from components.java
        }
    }
}