[Gradle] Fix switching in-process to Native embeddable compiler jar

Compiler runner used incorrect cache key for isolated classloader:
it didn't take the actually used compiler jar into account,
only the K/N home dir.

Fix this by using the entire classpath as a key.

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/compilerRunner/nativeToolRunners.kt

@@ -99,7 +99,10 @@ internal abstract class KotlinNativeToolRunner(
             """.trimIndent()
         }
 
-    final override val isolatedClassLoaderCacheKey get() = project.konanHome
+    data class IsolatedClassLoaderCacheKey(val classpath: Set<java.io.File>)
+
+    // TODO: can't we use this for other implementations too?
+    final override val isolatedClassLoaderCacheKey get() = IsolatedClassLoaderCacheKey(classpath)
 
     override fun transformArgs(args: List<String>) = listOf(toolName) + args