Note that this patch is Debian-specific as we know that libssh2 is linked
to gcrypt.
Patching configure.ac to add gpg-error as a dependent library is not good, as it
would cause overlinking of libssh2, and there is no separate variable for
"static dependencies".
All this mess ought to be solved in gcrypt inself by providing .pc file,
but it is not.
Gbp-Pq: Name 0001-Add-lgpg-error-to-.pc-to-facilitate-static-linking.patch
luoyaoming