How to execute a task before executing or building the subprojects in gradle?

I have created a sample project for this. The root project is called 'protobuffer' and it has two sub projects as follows:

• java-project
• proto

'proto' project contains proto files for the java project. proto project's build.gradle.kts file is as follows:

import com.google.protobuf.gradle.*

plugins {
    id ("com.google.protobuf")
}

tasks.check { dependsOn("generateProto") }

protobuf {
    protoc {
        artifact = "com.google.protobuf:protoc:3.6.1"
    }

    generatedFilesBaseDir = File(project(":java-project").projectDir.toString(), "src").toString()
}

dependencies {
    implementation("com.google.protobuf:protobuf-java:3.6.1")
}

Root project's build.gradle.kts file is as follows:

import com.google.protobuf.gradle.GenerateProtoTask
plugins {
    java
    id ("com.google.protobuf") version ("0.8.8") apply false
}

allprojects {
    repositories {
        mavenCentral()
        maven {
            url = uri("https://plugins.gradle.org/m2/")
        }
    }
}

subprojects {
    apply(plugin="java")
    apply(plugin="idea")

    if (name != "proto") {
        tasks.withType<JavaCompile> {
            dependsOn(project(":proto").tasks.withType<GenerateProtoTask>())
        }
    }
}

The settings.gradle.kts file in the root project is as follows:

rootProject.name = "protobuffer"
include("proto")
include("java-project")


pluginManagement {
    repositories {
        mavenLocal()
        maven {
            url = uri("https://plugins.gradle.org/m2/")
        }
    }

    resolutionStrategy {
        eachPlugin {
            if (requested.id.id == "com.google.protobuf") {
                useModule("com.google.protobuf:protobuf-gradle-plugin:${requested.version}")
            }
        }
    }
}