fate: Add a target for creating a 16000 Hz mono synthetic audio file

Signed-off-by: Martin Storsjö <martin@martin.st>

tests/Makefile

@@ -17,7 +17,11 @@ tests/data/asynth1.sw: tests/audiogen$(HOSTEXESUF)
 	@mkdir -p tests/data
 	$(M)./$< $@
 
-tests/data/asynth1.sw tests/vsynth%/00.pgm: TAG = GEN
+tests/data/asynth-16000-1.sw: tests/audiogen$(HOSTEXESUF)
+	@mkdir -p tests/data
+	$(M)./$< $@ 16000 1
+
+tests/data/asynth%.sw tests/vsynth%/00.pgm: TAG = GEN
 
 include $(SRC_PATH)/tests/fate.mak
 include $(SRC_PATH)/tests/fate2.mak