Link lib/libc/c063 tests to the build.

Some files lack required #include <sys/stat.h>. The #ifdef is per ngie's
request; the includes are clearly necessary for struct stat.

The faccessat test fails because it tries to use AT_SYMLINK_NOFOLLOW with
faccessat(), which is not specified by POSIX.1-2008.

Differential Revision: https://reviews.freebsd.org/D1411
Reviewed by: ngie