Sample USBserial project that compiles OK on Web Compiler, but breaks for GCC ARM

Dependencies:   USBDevice mbed

This code compiles on the online MBED compiler.

When Exported to GCC ARM it fails.

//when compiled with GCC_ARM we get the following issues which result in unresolved symbols
/*
    - The type 'USBSerial' must implement the inherited pure virtual method 
     'mbed::FileHandle::write'
    - The type 'USBSerial' must implement the inherited pure virtual method 
     'mbed::FileHandle::lseek'
    - The type 'USBSerial' must implement the inherited pure virtual method 
     'mbed::FileHandle::read'
*/