fate: Fix fate-ac3-fixed-encode for pre-ssse3 x86 machines

The default mmxext and sse implementations of apply_window_int16
aren't bitexact.
Signed-off-by: Martin Storsjö <martin@martin.st>

tests/fate/ac3.mak

@@ -49,7 +49,7 @@ fate-eac3-encode: FUZZ = 3
 FATE_AC3 += fate-ac3-fixed-encode
 fate-ac3-fixed-encode: tests/data/asynth-44100-2.wav
 fate-ac3-fixed-encode: SRC = $(TARGET_PATH)/tests/data/asynth-44100-2.wav
-fate-ac3-fixed-encode: CMD = md5 -i $(SRC) -c ac3_fixed -b 128k -f ac3
+fate-ac3-fixed-encode: CMD = md5 -i $(SRC) -c ac3_fixed -b 128k -f ac3 -flags bitexact
 fate-ac3-fixed-encode: CMP = oneline
 fate-ac3-fixed-encode: REF = a1d1fc116463b771abf5aef7ed37d7b1