I am using gradle 6.2 version with jdk 8 in my application, it's builing 2 jar files under build/libs/ directory. How can I create the single executable jar in my application?

My build.gradle,

```
plugins {
  id 'com.google.cloud.tools.jib' version '2.2.0'
  id 'application'
  id 'java'
}

repositories {
    mavenLocal()
    mavenCentral()
    jcenter()
}

jib.to.image = 'gcr.io/' + project.property('gcpProjectId') + '/my-application'
jib.container.creationTime = 'USE_CURRENT_TIMESTAMP'

mainClassName = "com.foo.Myapplication"

jar {
  manifest { 
    attributes "Main-Class": "$mainClassName"
  }  

  from {
    configurations.runtimeClasspath.collect { it.isDirectory() ? it : zipTree(it) }
  }
}

```

**Created Jar files:**

```
ls -ltr build/libs/
total 31184
-rw-r--r-- 1  user 15986229 Jun  9 20:22 my-application-1.0.0.jar
-rw-r--r-- 1  user 15942345 Jun  9 20:22 my-application-1.0.0-all.jar

```

Why it's creating -all.jar while executing "gradle clean build" ?
What did am wrong here?
Kindly provide your thoughts on this.