Revert "Use gradle toolchains in the buildscript"

This reverts commit 84ea864e

build.gradle.kts

@@ -32,7 +32,6 @@ version = "0.3.2"
 val groupAndName = "${rootProject.group}.${rootProject.name.toLowerCase()}"
 
 val javaVer: String = "8"
-val sourceJavaVer: String = "16"
 val kotlinVer: String by rootProject
 val kotlinBaseVer = kotlinVer.substring(0..2)
 val serializationVer: String by rootProject
@@ -41,10 +40,6 @@ val mcBase: String = (rootProject.property("minecraft") as String).also {
 }.substring(0..3)
 val kotlinX: String = "org.jetbrains.kotlinx"
 
-val toolchainJavaVersion = Action<JavaToolchainSpec> {
-    languageVersion.set(JavaLanguageVersion.of(sourceJavaVer.toInt()))
-}
-
 subprojects {
     group = rootProject.group.toString()
     apply(plugin = "org.cqfn.diktat.diktat-gradle-plugin")
@@ -196,8 +191,6 @@ allprojects {
     apply(plugin = "java")
     apply(plugin = "org.jetbrains.kotlin.jvm")
     apply(plugin = "architectury-plugin")
-    val compiler = javaToolchains.compilerFor(toolchainJavaVersion)
-    val launcher = javaToolchains.launcherFor(toolchainJavaVersion)
     dependencies {
         implementation(kotlin("stdlib-jdk8", kotlinVer))
         implementation(kotlin("reflect", kotlinVer))
@@ -205,7 +198,6 @@ allprojects {
     }
     tasks {
         withType(org.jetbrains.kotlin.gradle.tasks.KotlinCompile::class) {
-            kotlinJavaToolchain.toolchain.use(launcher)
             with(kotlinOptions) {
                 // https://github.com/JetBrains/kotlin/blob/master/compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/arguments/K2JVMCompilerArguments.kt
                 freeCompilerArgs = listOf(
@@ -224,10 +216,9 @@ allprojects {
                 encoding = "UTF-8"
                 isFork = true
                 release.set(javaVer.toInt())
-                javaCompiler.set(compiler)
-                sourceCompatibility = sourceJavaVer
+                sourceCompatibility = "11"
                 targetCompatibility = javaVer
-                compilerArgs.addAll(listOf("-Xplugin:jabel"))
+                compilerArgs.add("-Xplugin:jabel")
             }
         }
         withType(ProcessResources::class) {