Fix build

Test: build for sdk_phone_mips-sdk (mac) works
Change-Id: Ifc839975d1fc994beeb1651280e2d94e8b7a3199
diff --git a/audio_utils/fifo.cpp b/audio_utils/fifo.cpp
index 31a0c62..29c6642 100644
--- a/audio_utils/fifo.cpp
+++ b/audio_utils/fifo.cpp
@@ -51,9 +51,15 @@
 #endif  // __ANDROID__
 #else   // __linux__
 // macOS doesn't have clock_nanosleep
+typedef int clockid_t;
+#define CLOCK_MONOTONIC 0
 int clock_nanosleep(clockid_t clock_id, int flags, const struct timespec *request,
         struct timespec *remain)
 {
+    (void) clock_id;
+    (void) flags;
+    (void) request;
+    (void) remain;
     errno = ENOSYS;
     return -1;
 }