posix: tst-glob_lstat_compat no longer needs to be an internal test

compat_symbol_reference is now available for regular tests as well.
Also avoid building and running the tests in case the pre-2.27
symbol version of glob is not available.  This avoids a spurious
UNSUPPORTED result.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>