Try another fix

src/libFLAC/stream_encoder.c

@@ -49,10 +49,33 @@
 /* Mac does have sem_init, but it doesn't work */
 #include <dispatch/dispatch.h>
 typedef dispatch_semaphore_t sem_t;
-#define sem_init(sem,x,val) ((*sem = dispatch_semaphore_create(val)) == NULL)
-#define sem_post(sem) dispatch_semaphore_signal(*sem)
-#define sem_wait(sem) dispatch_semaphore_wait(*sem, DISPATCH_TIME_FOREVER)
-#define sem_destroy(sem) dispatch_release(*sem)
+static int sem_init(sem_t *sem, int is_shared, unsigned int value)
+{
+	(void)is_shared;
+	if((*sem = dispatch_semaphore_create (value)) == NULL)
+		return -1;
+	else
+		return 0;
+}
+
+static int sem_post(sem_t *sem)
+{
+	dispatch_semaphore_signal(*sem);
+	return 0;
+}
+
+static int sem_wait(sem_t *sem)
+{
+	dispatch_semaphore_wait(*sem, DISPATCH_TIME_FOREVER);
+	return 0;
+}
+
+static int sem_destroy(sem_t *sem)
+{
+	dispatch_release(*sem);
+	return 0;
+}
+
 #else
 #include <semaphore.h>
 #endif