security/gnutls: gnutls-3.8.8 requires llvm17 or higher to build

[Tatsuki Makino]

Hello.

It seems that it is mandatory to use llvm17 or higher to build gnutls 3.8.8.
If not, the following error cannot be resolved. Changing -std=c11 is powerless.

groups.c:93:2: error: initializer element is not a compile-time constant
        group_x25519,
        ^~~~~~~~~~~~

If you are still stuck with the old version, make a modification that uses 17 
or higher of clang 🤣

Regards.