gnupg: Fix reproducibility failure

yat2m can be found within the build or from the recipe-sysroot-native if
runtime dependencies are present. The sysroot version has version differences
to the in tree copy. Specify the one we want to make the build determinstic.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 1feb5274)
Signed-off-by: Steve Sakoman <steve@sakoman.com>