Build was configured to prefer settings repositories over project repositories but repository 'maven' was added by build file 'build.gradle'

I want to add jitpack.io as a repository in my gradle file. This is my gradle root file:

buildscript {
    repositories {
        google()
        mavenCentral()
    }
    dependencies {
        classpath "com.android.tools.build:gradle:7.0.2"
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:1.5.21"

        classpath 'com.google.dagger:hilt-android-gradle-plugin:2.38.1'

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}
task clean(type: Delete) {
    delete rootProject.buildDir
}

Since I DON'T have a "allrepositories" to put my dependency there (only works there), I've created and added this code after buildscript code:

allprojects {
    repositories {
        maven {url 'https://www.jitpack.io'}
    }
}

But this is the error I get

Caused by: org.gradle.api.InvalidUserCodeException: Build was configured to prefer settings repositories over project repositories but repository 'maven' was added by build file 'build.gradle'

General Info

Gradle 6.8 introduced central declaration of repositories, new way to define repositories. Latest documentation (7.4.2) can be found here.

You have 2 options from here;

Remove central declaration to work with your current config

For this you need to remove the dependencyResolutionManagement block from the setting.gradle file (=the new way). And then the repositories config in your build.gradle will work again (=the old way).

build.gradle (no change from your example)

allprojects {
    repositories {
        maven {url 'https://www.jitpack.io'}
    }
}

Update to work the new way

The way forward is to edit build.gradle removing that repositories declaration. And then edit settings.gradle to include the maven config.

settings.gradle

dependencyResolutionManagement {
    repositoriesMode.set(RepositoriesMode.FAIL_ON_PROJECT_REPOS)
    repositories {
        google()
        mavenCentral()
        maven { url 'https://jitpack.io' }
    }
}