How to configure spock in spring boot with gradle 6+ and java 11+

I want to use spock in my spring-boot project (using groovy, not java). I have some projects with spock already working in java 8 and lower versions of gradle but I can't find documentation about the newest versions.

This is my OLD build.gradle

    buildscript {
    ext {
        springBootVersion = '2.1.0.RELEASE'
    }
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
    }
}

apply plugin: 'groovy'
apply plugin: 'eclipse'
apply plugin: 'org.springframework.boot'
apply plugin: 'io.spring.dependency-management'

group = 'com.test'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = 1.8

repositories {
    mavenCentral()
}


dependencies {
    implementation('org.springframework.boot:spring-boot-starter-data-mongodb')
    implementation('org.springframework.boot:spring-boot-starter-web')
    implementation('org.codehaus.groovy:groovy')
    testImplementation('org.springframework.boot:spring-boot-starter-test')

    testCompile(
            'junit:junit:4.12',
            'org.codehaus.groovy:groovy-all:2.4.4',
            'org.spockframework:spock-core:1.2-groovy-2.4',
            'cglib:cglib:2.2',
            'org.spockframework:spock-spring:1.2-groovy-2.4',
    )
}

this works and I can create spock tests but when I create a project with java 11 and gradle 6.4, nothing works anymore (the gradle syntax is way different and the spock libraries don't work anymore),

this is my CURRENT (and failing) build.gradle:

plugins {
    id 'org.springframework.boot' version '2.3.2.RELEASE'
    id 'io.spring.dependency-management' version '1.0.9.RELEASE'
    id 'groovy'
}

group = 'com.test'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '11'

repositories {
    mavenCentral()
}

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-data-jpa'
    implementation 'org.springframework.boot:spring-boot-starter-security'
    implementation 'org.springframework.boot:spring-boot-starter-web'
    implementation 'org.codehaus.groovy:groovy'
    runtimeOnly 'com.h2database:h2'
    runtimeOnly 'org.postgresql:postgresql'


    testImplementation("org.spockframework:spock-core") {
        exclude group: "org.codehaus.groovy", module: "groovy-all"

    }
    testImplementation group: 'org.spockframework', name: 'spock-spring', version: '2.0-M3-groovy-3.0'
    testImplementation(enforcedPlatform("org.spockframework:spock-bom:2.0-M1-groovy-2.5"))
}

test {
    useJUnitPlatform()
}

With this, nothing works but the gradle build doesn't found the spock-spring libraries.

How can I apply the spock libraries to spring boot with the newest versions of java and gradle?