PortAudio: Disable sndio in PortAudio to avoid missing -lsndio errors

Fixes a compilation error introduced in sysprog21#76, where the `make all` target fails
during the build of the PortAudio library on GNU/Linux systems.

The failure was caused by PortAudio's configure script automatically enabling
the sndio backend when `libsndio-dev` headers are present, which leads to
linker errors due to missing `-lsndio`.

To avoid this, we now explicitly pass `--without-sndio` to PortAudio’s
configure script. This ensures that sndio support is disabled regardless of
system headers, eliminating the need for `-lsndio` and fixing the build.

Author: shengwen-tw

Makefile

@@ -100,7 +100,7 @@ ifeq ($(call has, VIRTIOSND), 1)
 portaudio/Makefile:
 	git submodule update --init portaudio
 $(PORTAUDIOLIB): portaudio/Makefile
-	cd $(dir $<) && ./configure
+	cd $(dir $<) && ./configure --without-sndio
 	$(MAKE) -C $(dir $<)
 main.o: $(PORTAUDIOLIB)