utils/fs: use <sys/stat.h>, not <sys\stat.h>

Authored by trofi on May 14 2018, 3:09 AM.

Description

utils/fs: use <sys/stat.h>, not <sys\stat.h>

Fix cross-compilation failure from linux to windows:

  CC utils/unlit/dist-install/build/fs.o
utils/unlit/fs.c:24:10: fatal error: sys\stat.h: No such file or directory
 #include <sys\stat.h>
          ^~~~~~~~~~~~

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>