libgpgme: disable all tests

Disable all of the tests, including runtime that needs gnupg.
There's no longer --without configure options for them, it's now
--disable. Fixes:
http://autobuild.buildroot.net/results/eb1/eb1e06b1d99c441b6086c07ee04b084a61041dc7/



Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>