The code uses ssize_t which is usually defined in <unistd.h>

Signed-off-by: Alex Suykov <alex.suykov@gmail.com>

--- a/host/lib/fmap.c
+++ a/host/lib/fmap.c
@@ -6,6 +6,7 @@
 
 #include <stdio.h>
 #include <string.h>
+#include <unistd.h>
 
 #include "fmap.h"