For the users, it looks a little bit weird that capstone and slirp are
not disabled automatically if they run the configure script with the
"--without-default-features" option, so let's do that now.
Note: fdt is *not* changed accordingly since this affects the targets
that we can build, so disabling fdt automatically here might have
unexpected side-effects for the users.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Acked-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220221090647.150184-1-thuth@redhat.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>