Fix #2218: NoSuchMethodError when parsing a JSON stream on Java 8

Author: madhead

formats/json/jvmMain/src/kotlinx/serialization/json/internal/CharsetReader.kt

@@ -20,7 +20,7 @@ internal class CharsetReader(
             .onMalformedInput(CodingErrorAction.REPLACE)
             .onUnmappableCharacter(CodingErrorAction.REPLACE)
         byteBuffer = ByteBuffer.wrap(ByteArrayPool8k.take())
-        byteBuffer.flip() // Make empty
+        (byteBuffer as Buffer).flip() // Make empty
     }
 
     @Suppress("NAME_SHADOWING")
@@ -92,7 +92,7 @@ internal class CharsetReader(
             if (bytesRead < 0) return bytesRead
             byteBuffer.position(position + bytesRead)
         } finally {
-            byteBuffer.flip()
+            (byteBuffer as Buffer).flip()
         }
         return byteBuffer.remaining()
     }