xmlstarlet: fix static linking

Make sure we take into account libgpg-error when linking against
libgcrypt, by adding a patch against xmlstarlet configure.ac. The
handling of static libraries is clearly horrible in this configure.ac
script, using pkg-config would be a lot better, but it's also a lot
more work.

Fixes:

  http://autobuild.buildroot.org/results/931/931dede013d94f88fcb5185dac494775603063ec/



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>