[PATCH] avoid gpgtar.test when --disable-gpgtar is configured

[Justus Winter]

Hi,

Quoting Daniel Kahn Gillmor (2016-02-04 22:07:38)
>         $(sqlite3_dependent_tests) \
> -       gpgtar.test use-exact-key.test default-key.test \
> +       $(gpgtar_tests) use-exact-key.test default-key.test \

I don't like it.  I know that we do the same for the tofu test.  There
is a better way to skip a test, just return 77.

Thanks,
Justus