Build audio.usb.default with BOARD_VNDK_VERSION

Bug: 37342627
Test: BOARD_VNDK_VERSION=current m -j64 audio.usb.default
Change-Id: I0be8ad7283e200bf36100eca38b28af4220530fd
Merged-In: I0be8ad7283e200bf36100eca38b28af4220530fd
diff --git a/modules/usbaudio/audio_hal.c b/modules/usbaudio/audio_hal.c
index df4bc0f..e93396f 100644
--- a/modules/usbaudio/audio_hal.c
+++ b/modules/usbaudio/audio_hal.c
@@ -23,6 +23,7 @@
 #include <stdint.h>
 #include <stdlib.h>
 #include <sys/time.h>
+#include <unistd.h>
 
 #include <log/log.h>
 #include <cutils/list.h>