Build: Add auto-setup of JDKs for tests based on Gradle Java Toolchains

buildSrc/src/main/kotlin/JvmToolchain.kt

@@ -26,6 +26,8 @@ enum class JdkMajorVersion(
 
     fun isMandatory(): Boolean = mandatory
 
+    val envName = name
+
     companion object {
         fun fromMajorVersion(majorVersion: Int) = values().first { it.majorVersion == majorVersion }
     }

buildSrc/src/main/kotlin/tasks.kt

@@ -248,6 +248,12 @@ fun Project.projectTest(
                 project.providers.gradleProperty("kotlin.test.maxParallelForks").forUseAtConfigurationTime().orNull?.toInt()
                     ?: forks.coerceIn(1, Runtime.getRuntime().availableProcessors())
         }
+
+        JdkMajorVersion.values().forEach { version ->
+            project.getToolchainLauncherFor(version).orNull?.let {
+                environment(version.envName, it.metadata.installationPath.asFile.absolutePath)
+            }
+        }
     }.apply { configure(body) }
 }