package/espeak: don't override dependencies

Don't override ESPEAK_DEPENDENCIES in a conditional

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/espeak/espeak.mk

@@ -13,11 +13,11 @@ ESPEAK_LICENSE_FILES = License.txt
 
 ifeq ($(BR2_PACKAGE_ESPEAK_AUDIO_BACKEND_ALSA),y)
 ESPEAK_AUDIO_BACKEND = portaudio
-ESPEAK_DEPENDENCIES = portaudio
+ESPEAK_DEPENDENCIES += portaudio
 endif
 ifeq ($(BR2_PACKAGE_ESPEAK_AUDIO_BACKEND_PULSEAUDIO),y)
 ESPEAK_AUDIO_BACKEND = pulseaudio
-ESPEAK_DEPENDENCIES = pulseaudio
+ESPEAK_DEPENDENCIES += pulseaudio
 endif
 
 define ESPEAK_EXTRACT_CMDS