buildSrc, kotlin-dsl plugin: suppress experimentalWarning

This warning is about https://docs.gradle.org/current/userguide/kotlin_dsl.html#sec:kotlin-dsl_plugin.

It appears after we are strating using our bootstrap plugin for buildSrc
 too. It is unlikely that new compiler will broke build scripts
 compilation for our project, so we can suppress it.

buildSrc/build.gradle.kts

@@ -56,6 +56,10 @@ gradlePlugin {
     }
 }
 
+kotlinDslPluginOptions {
+    experimentalWarning.set(false)
+}
+
 fun Project.getBooleanProperty(name: String): Boolean? = this.findProperty(name)?.let {
     val v = it.toString()
     if (v.isBlank()) true