[3.0.x] contrib/gnutls: fix AArch64 build on appleOS

This introduces a patch to fix compilation on AArch64 on AppleOS, which currently fails due to a compiler flag used by gnutls that is unsupported by the latest version of clang (Apple clang version 13.1.6, clang-1316.0.21.2) leading to a compiler crash if used.

This resolves the upstream tickets https://gitlab.com/gnutls/gnutls/-/issues/1347 and https://gitlab.com/gnutls/gnutls/-/issues/1317 for which the same patch was already suggested.

(cherry picked from commit 85357e2d, backport of !1678 (merged))