We have been using `uint8_t *`, which works fine as far as
linking goes, but leads fuzz target developers to sometimes
forget why they can't just modify the passed in string instead of
copying it for modification (e.g. to NUL-terminate).

REF: https://llvm.org/docs/LibFuzzer.html#fuzz-target

Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>

LibFuzzer, Honggfuzz and other programs implement simple interfaces for
fuzzing appropriately prepared code. Samba contains quite a lot of
parsing code, often a good target for fuzzing.

With this change the build system is amended to support building fuzzing
binaries (added in later changes).

Signed-off-by: Michael Hanselmann <public@hansmi.ch>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>