Get back some functional of "trying to update up to gradle wrapper 8.1.1"

repos/generator/build.gradle

@@ -14,3 +14,12 @@ dependencies {
     api libs.kotlin.poet
     api libs.ksp
 }
+
+kotlin {
+    jvmToolchain(8)
+}
+
+java {
+    sourceCompatibility = JavaVersion.VERSION_1_8
+    targetCompatibility = JavaVersion.VERSION_1_8
+}