Build: Drop unused setupBuildCache helper

dependencies/kotlin-build-gradle-plugin/src/BuildCache.kt

@@ -1,24 +0,0 @@
-/*
- * Copyright 2010-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
- * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
- */
-
-import org.gradle.api.initialization.Settings
-import org.gradle.caching.http.HttpBuildCache
-import java.net.URI
-
-
-fun Settings.setupBuildCache() {
-    buildCache.local.isEnabled = kotlinBuildProperties.localBuildCacheEnabled
-    kotlinBuildProperties.localBuildCacheDirectory?.let { buildCache.local.directory = it }
-    kotlinBuildProperties.buildCacheUrl?.let { remoteCacheUrl ->
-        buildCache.remote(HttpBuildCache::class.java) { remoteCache ->
-            remoteCache.url = URI(remoteCacheUrl)
-            remoteCache.isPush = kotlinBuildProperties.pushToBuildCache
-            if (kotlinBuildProperties.buildCacheUser != null && kotlinBuildProperties.buildCachePassword != null) {
-                remoteCache.credentials.username = kotlinBuildProperties.buildCacheUser
-                remoteCache.credentials.password = kotlinBuildProperties.buildCachePassword
-            }
-        }
-    }
-}