You have to add host-alsa-lib and host-pulseaudio to the QEMU_DEPENDENCIES for this to work. Buildroot does not want to depend on anything pre-installed on the host (if you're OK with stuff that is pre-installed on the host, you can just as well install qemu-system-arm, right?)

Of course, currently there is no host package for alsa-lib or pulseaudio, so you'll have to add them first. And pulsaudio has dependencies for which no host package exits either, so this will take a bit of work...

I have extracted the configuration of the libpulse and alsa from the system pkgconf:

$ pkgconf libpulse --libs 
-L/usr/lib/x86_64-linux-gnu -lpulse
$ pkgconf libpulse --cflags
-D_REENTRANT 
$ pkg-config alsa --libs
-L/usr/lib/x86_64-linux-gnu -lasound 
$ pkg-config alsa --cflags


Then I have injected them by hand to the "configure" script in the output/build/host-qemu-5.2.0/ :


##########################################
# Sound support libraries probe

audio_drv_list=$(echo "$audio_drv_list" | sed -e 's/,/ /g')
for drv in $audio_drv_list; do
    case $drv in
    alsa | try-alsa)
    if true; then
        alsa_libs="-L/usr/lib/x86_64-linux-gnu -lasound"
        alsa_cflags=""
        alsa=yes
        if test "$drv" = "try-alsa"; then
            audio_drv_list=$(echo "$audio_drv_list" | sed -e 's/try-alsa/alsa/')
        fi
    else
        if test "$drv" = "try-alsa"; then
            audio_drv_list=$(echo "$audio_drv_list" | sed -e 's/try-alsa//')
        else
            error_exit "$drv check failed" \
                "Make sure to have the $drv libs and headers installed."
        fi
    fi
    ;;

    pa | try-pa)
    if true; then
        libpulse=yes
        pulse_libs="-L/usr/lib/x86_64-linux-gnu -lpulse"
        pulse_cflags="-D_REENTRANT"
        if test "$drv" = "try-pa"; then
            audio_drv_list=$(echo "$audio_drv_list" | sed -e 's/try-pa/pa/')
        fi
    else
        if test "$drv" = "try-pa"; then
            audio_drv_list=$(echo "$audio_drv_list" | sed -e 's/try-pa//')
        else
            error_exit "$drv check failed" \
                "Make sure to have the $drv libs and headers installed."
        fi
    fi
    ;;

After that, and with the following:

# Override CPP, as it expects to be able to call it like it'd
# call the compiler.
define HOST_QEMU_CONFIGURE_CMDS
	unset TARGET_DIR; \
	cd $(@D); $(HOST_CONFIGURE_OPTS) CPP="$(HOSTCC) -E" \
		./configure \
		--target-list="$(HOST_QEMU_TARGETS)" \
		--prefix="$(HOST_DIR)" \
		--interp-prefix=$(STAGING_DIR) \
		--cc="$(HOSTCC)" \
		--host-cc="$(HOSTCC)" \
		--extra-cflags="$(HOST_QEMU_CFLAGS)" \
		--extra-ldflags="$(HOST_LDFLAGS)" \
		--audio-drv-list="alsa,pa,oss" \
		--meson=$(HOST_DIR)/bin/meson \
		--ninja=$(HOST_DIR)/bin/ninja \
		--disable-bzip2 \
		--disable-containers \
		--disable-curl \
		--disable-libssh \
		--disable-linux-io-uring \
		--disable-sdl \
		--disable-vhost-user-blk-server \
		--disable-virtiofsd \
		--disable-vnc-jpeg \
		--disable-vnc-png \
		--disable-vnc-sasl \
		--disable-tests \
		$(HOST_QEMU_OPTS)
endef

in the package/qemu/qemu.mk , I was able to compile QEMU with supported alsa and pa drivers:

./qemu-system-aarch64 --audio-help
Environment variable based configuration deprecated.
Please use the new -audiodev option.

Equivalent -audiodev to your current environment variables:
(Since you didn't specify QEMU_AUDIO_DRV, I'll list all possibilities)
-audiodev id=alsa,driver=alsa
-audiodev id=pa,driver=pa
-audiodev id=oss,driver=oss
-audiodev id=none,driver=none

It is an awful workaround, but at least it works...

(In reply to Arnout Vandecappelle from comment #1)
Unfortunately we have to use the patched QEMU (to add the GUI-connected GPIO emulation for our students - http://koral.ise.pw.edu.pl/~wzab/artykuly/Teaching_electronics_disease_virtual_lab.pdf ).
The version for BR 2021.02 is in https://github.com/wzab/BR_Internet_Radio/tree/gpio_simple_2021.02/QemuVirt64

Created attachment 8926 [details]
Patch with temporary work-around

Created attachment 8931 [details]
Patch with temporary work-around

This is a temporary work-around - a patch to the qemu package.
It simply switches to using the standard pkg-config, when the sound libraries are detected and configured. After that the original Buildroot-provided pkg-config is restored.
The correct operation is confirmed on Debian/testing.

The temporary workaround is also available in the BR_Internet_Radio:

https://github.com/wzab/BR_Internet_Radio/commit/bdf7afed292ec0408fe908df42a4bc298031141a

https://github.com/wzab/BR_Internet_Radio/commit/2117504dc040cdc679e379eee87cde3c498c694d

Thank you for your report.

The issue tracker for the Buildroot project has been moved to
the Gitlab.com issue tracker:
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