main/alsa-lib: enable asserts again

The --without-debug flag was added silently in e7099738. As per ./configure --help, this flag disables assert statements in alsa-lib. This is undesirable since it makes library usage errors more laborious to debug or potentially even makes them go unnoticed.

For example, see #12729 (closed) where a null pointer was passed to snd_config_delete by alsa-utils. While the snd_config_delete function in alsa-lib contains an assert checking that the passed config is non-null this assert was disabled due to the aforementioned configure flag.

See also:

• https://lists.alpinelinux.org/~alpine/devel/%3C1ZU8S8ERRPKR9.35CUIBSS8QET7%408pit.net%3E