Downgrade from java 11 to java 1.8

Hello,
for compatibility issues, could it be possible to downgrade from java 11 to 1.8?

```kotlin
  compileOptions {
    sourceCompatibility = JavaVersion.VERSION_11
    targetCompatibility = JavaVersion.VERSION_11
  }
``` 

```kotlin
  jvmToolchain(11)
``` 

Snippets from your `build.gradle.kts`.
Regards!