qt5multimedia: conditionally add alsa-lib to dependencies

Qt5Multimedia builds the alsa plugin if it detects libasound in the
system. Add alsa-lib to dependencies if BR2_PACKAGE_ALSA_LIB is
selected.

Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Reviewed-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
(cherry picked from commit 8d7dd837e5e2fcc7b785472e7215ffa74b546d9c)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/qt5/qt5multimedia/qt5multimedia.mk

@@ -30,6 +30,10 @@ ifeq ($(BR2_PACKAGE_LIBGLIB2)$(BR2_PACKAGE_PULSEAUDIO),yy)
 QT5MULTIMEDIA_DEPENDENCIES += libglib2 pulseaudio
 endif
 
+ifeq ($(BR2_PACKAGE_ALSA_LIB),y)
+QT5MULTIMEDIA_DEPENDENCIES += alsa-lib
+endif
+
 define QT5MULTIMEDIA_CONFIGURE_CMDS
 	(cd $(@D); $(TARGET_MAKE_ENV) $(HOST_DIR)/usr/bin/qmake)
 endef