package/gnupg2: really do not run tests in cross-compilation

gnupg2 still tries to run test even if it tries to avoid it in
cross-compilation.

Really disable running the tests.

Since that requires a complete autoreconf, the existing patch against
configure is turned into a patch against the m4 macro.

since we autoreconf, we slightly patch configure.ac to not emit git
errors on stderr because it is not in a git tree.

[Thomas: rename patch 0000 to 0004, as suggested by Arnout.]

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>