gnupg: disable tests to avoid running target binaries at build time

gnupg: disable tests to avoid running target binaries at build time

By default, the tests are built and run at do_compile and we can see
errors like below in log.do_compile:

  gnupg-2.4.4/tests/cms/inittests: line 99: ../../sm/gpgsm: cannot execute binary file: Exec format error

Note that the do_compile process still succeeds. However, we'd better avoid
executing these target binaries at build time.

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>