Do not depend on BaseFileObject type for incremental KAPT

This class does not exist in JDK9, so running incremental KAPT on
JDK9 fails. Because it is used only to get the name of the file,
this has been replaced with usage of the public JavaFileObject API.

plugins/kapt3/kapt3-base/src/org/jetbrains/kotlin/kapt3/base/javac/KaptJavaFileManager.kt

@@ -5,7 +5,6 @@
 
 package org.jetbrains.kotlin.kapt3.base.javac
 
-import com.sun.tools.javac.file.BaseFileObject
 import com.sun.tools.javac.file.JavacFileManager
 import com.sun.tools.javac.main.Option
 import com.sun.tools.javac.util.Context
@@ -66,8 +65,7 @@ class KaptJavaFileManager(context: Context) : JavacFileManager(context, true, nu
         return when (fileObject.toUri().scheme) {
             "jar", "zip" -> false
             else -> {
-                if (fileObject !is BaseFileObject) return false
-                val typeName = packageName?.let { "$it." } + fileObject.shortName.dropLast(".class".length)
+                val typeName = packageName?.let { "$it." } + File(fileObject.toUri()).name.dropLast(".class".length)
 
                 return typeToIgnore.contains(typeName)
             }