Add missing include of <unistd.h>

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@149035 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Rewrite/FrontendActions.cpp b/lib/Rewrite/FrontendActions.cpp
index c1568cd..66affb0 100644
--- a/lib/Rewrite/FrontendActions.cpp
+++ b/lib/Rewrite/FrontendActions.cpp
@@ -23,6 +23,8 @@
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/FileSystem.h"
+#include <unistd.h>
+
 using namespace clang;
 
 //===----------------------------------------------------------------------===//