title: Set language level in Gradle and IntelliJ
body: <p>I've set the language level to 8 in the IntelliJ project settings, and I've also tried setting it in gradle like this:</p>
  
  <pre><code>   buildscript {
      ext.kotlinVersion = '1.3.41'
  
      repositories {
          mavenLocal()
          mavenCentral()
          maven { url "https://plugins.gradle.org/m2/" }
          maven { url "https://oss.sonatype.org/content/repositories/snapshots/" }
          jcenter()
          google()
      }
      dependencies {
          classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlinVersion"
  
      }
  
  }
  
  allprojects {
  
      version = '1.0'
      ext {
          appName = "VolumeFlux"
          gdxVersion = '1.9.10'
          roboVMVersion = '2.3.8'
          box2DLightsVersion = '1.4'
          ashleyVersion = '1.7.0'
          aiVersion = '1.8.0'
          visuiVersion = '1.4.2'
      }
  
      repositories {
          mavenLocal()
          mavenCentral()
          jcenter()
          google()
          maven { url "https://oss.sonatype.org/content/repositories/snapshots/" }
          maven { url "https://oss.sonatype.org/content/repositories/releases/" }
      }
  
  
      apply plugin: 'java'
      sourceCompatibility = 1.8
      targetCompatibility = 1.8
  
  }
  
  sourceCompatibility = 1.8
  targetCompatibility = 1.8
  
  subprojects {
      apply plugin: 'java'
      sourceCompatibility = 1.8
      targetCompatibility = 1.8
  }
  
  project(":desktop") {
      apply plugin: "kotlin"
  
      dependencies {
          implementation project(":core")
          api "com.badlogicgames.gdx:gdx-backend-lwjgl:$gdxVersion"
          api "com.badlogicgames.gdx:gdx-platform:$gdxVersion:natives-desktop"
          api "com.badlogicgames.gdx:gdx-box2d-platform:$gdxVersion:natives-desktop"
          api "com.badlogicgames.gdx:gdx-freetype-platform:$gdxVersion:natives-desktop"
          api "com.badlogicgames.gdx:gdx-tools:$gdxVersion"
          api "org.jetbrains.kotlin:kotlin-stdlib:$kotlinVersion"
      }
  }
  
  project(":core") {
      apply plugin: "kotlin"
  
      dependencies {
          api "com.badlogicgames.gdx:gdx:$gdxVersion"
          api "com.badlogicgames.gdx:gdx-box2d:$gdxVersion"
          api "com.badlogicgames.gdx:gdx-freetype:$gdxVersion"
          api "com.kotcrab.vis:vis-ui:1.3.0"
          api "com.github.czyzby:gdx-kiwi:1.9.1.9.6"
          api "net.dermetfan.libgdx-utils:libgdx-utils:0.13.4"
          api "com.badlogicgames.ashley:ashley:$ashleyVersion"
          api "org.jetbrains.kotlin:kotlin-stdlib:$kotlinVersion"
  
          compile "com.kotcrab.vis:vis-ui:$visuiVersion"
  
      }
  }
  </code></pre>
  
  <p>But for some reason I still get a gradle build error:</p>
  
  <pre><code>...\VolumeFlux.java:79: error: lambda expressions are not supported in -source 7
                  stockButtons.forEach(b -&gt; {
                                         ^
    (use -source 8 or higher to enable lambda expressions)
  </code></pre>