Update gradle version to 8.1 (#319)

* Updated Gradle version to 8.1. This was necessary as part of preparation of kotlinx.atomicfu for K2. Expected Gradle version to be compatible with K2 is 8.3, so it was decided to steadily update Gradle version first on develop and then try out the 8.3-nightly version in k2/dev branch.

* Removed deprecated experimentalWarning from kotlinDslOptions.

Author: mvicsokolova

build.gradle

@@ -73,8 +73,9 @@ allprojects {
     // This fixes "org.gradle.jvm.version" in Gradle metadata
     plugins.withType(JavaPlugin) {
         java {
-            sourceCompatibility = JavaVersion.VERSION_1_8
-            targetCompatibility = JavaVersion.VERSION_1_8
+            toolchain {
+                languageVersion.set(JavaLanguageVersion.of(8))
+            }
         }
     }
 }

buildSrc/build.gradle.kts

@@ -8,7 +8,3 @@ plugins {
 repositories {
     mavenCentral()
 }
-
-kotlinDslPluginOptions {
-    experimentalWarning.set(false)
-}

gradle/wrapper/gradle-wrapper.properties

@@ -2,4 +2,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-7.3-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.1-all.zip