[MIPS] Include header file unistd.h

required by unlink()

Change-Id: I4893cd5b341fc7965f5a1f68e55ffcbd037762b9
Signed-Off-By: Bhanu Chetlapalli <bhanu@mips.com>
diff --git a/lib/ExecutionEngine/Script.cpp b/lib/ExecutionEngine/Script.cpp
index 29e3898..f772c64 100644
--- a/lib/ExecutionEngine/Script.cpp
+++ b/lib/ExecutionEngine/Script.cpp
@@ -40,6 +40,7 @@
 #include <errno.h>
 #include <sys/stat.h>
 #include <sys/types.h>
+#include <unistd.h>
 
 #include <new>
 #include <string.h>