The sandbox is built with the SDL2 library with invokes the X11 library
which in turn calls getc(). But getc() in glibc is defined as

    int getc(FILE *)

This does not match our definition.

    int getc(void)

The sandbox crashes when called with parameter -l.

Rename our library symbol getc() to getchar().
Signed-off-by: NHeinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: NTom Rini <trini@konsulko.com>
Reviewed-by: NSimon Glass <sjg@chromium.org>