Change generated cache dir name according to change in Big Kotlin

The cache directory naming will be changed in the Big Kotlin repo.
This patch takes these changes into account and renames the cache
directory generated during the build.

Corresponding commit in the Big Kotlin:
https://github.com/JetBrains/kotlin/commit/ce2446f80fac6ec088eedd32c7b2e6cfae012e8c

platformLibs/build.gradle

@@ -65,7 +65,7 @@ project.rootProject.ext.platformManager.enabled.each { target ->
         task "${targetName}StdlibCache"(type: KonanCacheTask) {
             it.target = targetName
             originalKlib = file("$konanHome/klib/common/stdlib")
-            cacheDirectory = file("$konanHome/klib/cache/$targetName-g")
+            cacheRoot = file("$konanHome/klib/cache")
 
             dependsOn ":${targetName}CrossDist"
         }
@@ -106,7 +106,7 @@ project.rootProject.ext.platformManager.enabled.each { target ->
             task "${libName}Cache"(type: KonanCacheTask) {
                 it.target = targetName
                 originalKlib = tasks[libName].installDir
-                cacheDirectory = file("$konanHome/klib/cache/$targetName-g")
+                cacheRoot = file("$konanHome/klib/cache")
 
                 dependsOn "${targetName}StdlibCache"
                 dependsOn tasks[libName]

tools/kotlin-native-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/konan/tasks/KonanCacheTask.kt

@@ -3,10 +3,8 @@ package org.jetbrains.kotlin.gradle.plugin.konan.tasks
 import org.gradle.api.DefaultTask
 import org.gradle.api.tasks.*
 import org.jetbrains.kotlin.gradle.plugin.konan.KonanCompilerRunner
-import org.jetbrains.kotlin.gradle.plugin.tasks.KonanTargetableTask
 import org.jetbrains.kotlin.konan.target.CompilerOutputKind
 import org.jetbrains.kotlin.konan.target.HostManager
-import org.jetbrains.kotlin.konan.target.KonanTarget
 import java.io.File
 
 enum class KonanCacheKind(val outputKind: CompilerOutputKind) {
@@ -20,11 +18,16 @@ open class KonanCacheTask: DefaultTask() {
 
     // Taken into account by the [cacheFile] property.
     @Internal
-    lateinit var cacheDirectory: File
+    lateinit var cacheRoot: File
 
     @get:Input
     lateinit var target: String
 
+    @get:Internal
+    // TODO: Reuse NativeCacheKind from Big Kotlin plugin when it is available.
+    val cacheDirectory: File
+        get() = cacheRoot.resolve("$target-g$cacheKind")
+
     @get:OutputFile
     protected val cacheFile: File
         get() {