pakcage/sdl_mixer: add optional dependency on FluidSynth for MIDI

Add support for MIDI playback using FluidSynth.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/sdl_mixer/sdl_mixer.mk

@@ -22,11 +22,20 @@ SDL_MIXER_AUTORECONF = YES
 SDL_MIXER_CONF_OPTS = \
 	--without-x \
 	--with-sdl-prefix=$(STAGING_DIR)/usr \
-	--disable-music-midi \
 	--disable-music-mod \
 	--disable-music-mp3 \
 	--disable-music-flac # configure script fails when cross compiling
 
+ifeq ($(BR2_PACKAGE_FLUIDSYNTH),y)
+SDL_MIXER_DEPENDENCIES += fluidsynth
+SDL_MIXER_CONF_OPTS += \
+	--enable-music-midi \
+	--enable-music-fluidsynth-midi
+else
+SDL_MIXER_CONF_OPTS += \
+	--disable-music-midi
+endif
+
 ifeq ($(BR2_PACKAGE_LIBMAD),y)
 SDL_MIXER_CONF_OPTS += --enable-music-mp3-mad-gpl
 SDL_MIXER_DEPENDENCIES += libmad