Meson does not yet know to build our fuzzers. Introduce a new build
option "fuzzers" and wire up the fuzzers in case it is enabled. Adapt
our CI jobs so that they build the fuzzers by default.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
