warning: unlink is not implemented and will always fail

I get this message when I build a custom Simple Socket Server project in Nios2 SBT 11.0sp1. The build completes without error, but the app will not run. If I make a change in the app, for example turning on the VFS, it compiles without this message and runs fine. May be something to do with the custom part of the code, but how do I troubleshoot this?

Here is the entire warning message:

c:/altera/11.0/nios2eds/bin/gnu/h-i686-mingw32/bin/../lib/gcc/nios2-elf/4.1.2/../../../../nios2-elf/lib\libc.a(lib_a-unlinkr.o): In function `_unlink_r':

/build/swbuild/SJ/nightly/11.0sp1/208/l32/work/ip/sopc/app/gnu/BUILD/gnu/build-0-newlib.nios2-elf.i686-mingw32/nios2-elf/newlib/libc/reent/../../../../../src/newlib-1.16/newlib/libc/reent/unlinkr.c:54: warning: warning: unlink is not implemented and will always fail

Can anyone shed some light on this form me?