Log4j2.properties file not picked up in Gradle Java application?

I'm using the Gradle application plugin and trying to configure logging through SLF4J with a Log4J 2 implementation. I've put a log4j2.properties file in src/main/resources:

.
├── app
│   ├── build
│   │   ├── classes
│   │   │   └── java
│   │   │       └── main
│   │   │           └── log4j
│   │   │               └── App.class
│   │   ├── generated
│   │   │   └── sources
│   │   │       ├── annotationProcessor
│   │   │       │   └── java
│   │   │       │       └── main
│   │   │       └── headers
│   │   │           └── java
│   │   │               └── main
│   │   ├── resources
│   │   │   └── main
│   │   │       └── log4j2.properties
│   │   └── tmp
│   │       └── compileJava
│   │           └── source-classes-mapping.txt
│   ├── build.gradle
│   └── src
│       ├── main
│       │   ├── java
│       │   │   └── log4j
│       │   │       └── App.java
│       │   └── resources
│       │       └── log4j2.properties
│       └── test
│           ├── java
│           │   └── log4j
│           │       └── AppTest.java
│           └── resources
├── gradle
│   └── wrapper
│       ├── gradle-wrapper.jar
│       └── gradle-wrapper.properties
├── gradlew
├── gradlew.bat
└── settings.gradle

My build.gradle contains the Log4j 2 SLF4J binding (https://logging.apache.org/log4j/2.x/log4j-slf4j-impl/):

/*
 * This file was generated by the Gradle 'init' task.
 *
 * This generated file contains a sample Java application project to get you started.
 * For more details take a look at the 'Building Java & JVM projects' chapter in the Gradle
 * User Manual available at https://docs.gradle.org/6.8.1/userguide/building_java_projects.html
 */

plugins {
    // Apply the application plugin to add support for building a CLI application in Java.
    id 'application'
}

repositories {
    // Use JCenter for resolving dependencies.
    jcenter()
}

dependencies {
    // Use JUnit test framework.
    testImplementation 'junit:junit:4.13'

    // This dependency is used by the application.
    implementation 'com.google.guava:guava:29.0-jre'

    implementation group: 'org.slf4j', name: 'slf4j-api', version: '2.0.0-alpha1'
    implementation 'org.apache.logging.log4j:log4j-slf4j18-impl:2.14.0'

    compileOnly 'org.projectlombok:lombok:1.18.16'
    annotationProcessor 'org.projectlombok:lombok:1.18.16'

    testCompileOnly 'org.projectlombok:lombok:1.18.16'
    testAnnotationProcessor 'org.projectlombok:lombok:1.18.16'
}

application {
    // Define the main class for the application.
    mainClass = 'log4j.App'
}

and the App.java reads

package log4j;

import lombok.extern.slf4j.Slf4j;

@Slf4j
public class App {
    public String getGreeting() {
        return "Hello World!";
    }

    public static void main(String[] args) {
        log.debug("Printing a greeting...");
        System.out.println(new App().getGreeting());
    }
}

and app/src/main/resources contains the following:

# Define the root logger with appender file
log4j.rootLogger = DEBUG, stdout

log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%p\t%d{ISO8601}\t%r\t%c\t[%t]\t%m%n

Thus, I would expect the log level to get set to DEBUG and something to get printed to the console if I log.debug() in the application. However, if I ./gradlew run the application I don't see a log line:

> ./gradlew run

> Task :app:run
Hello World!

BUILD SUCCESSFUL in 953ms
3 actionable tasks: 1 executed, 2 up-to-date

However, I see no such log line, suggesting that the configuration file wasn't 'picked up'. How can I get this Java application to pick up the log4j2.properties file?