sdl.c is compiled against the SDL library.
Trying to redefine wchar_t with -fshort-wchar is not necessary
and leads to build failures when compiling against musl.
Cc: Milan P. Stanić <mps@arvanta.net>
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Simon Glass <sjg@chromium.org>