thank you for your help ... when I removed the files the hello work compiles (not tested, because I'm currently traveling and do not have access to my development board.
But when I use the SDFileSystem lib in my main project (with many other libraries) with the build flag I get two errors:
in file mbed.h "filesystem/FileSystem.h" not found. I fond it under Features. So I copied the complete folder one level down to Framework_mbed
Then in file FileSystem.h it can't find #include "BlockDevice.h" so I changed this line to #include "filesystem/bd/BlockDevice.h"
Now It compiles, Yeah! , but not tested ... I know that this is a crude hack but that is everything I can do. Can only do real tests on the board over the weekend.
The reason perhaps is that I use a TFT Display Lib which uses the File System Library to for loading bitmaps (#include "SPI_TFT_ILI9341.h")
Thank you for your help so far.