https://bugs.gentoo.org/426368
 
 IlmCtl/CtlInterpreter.cpp | 1 +
 1 file changed, 1 insertion(+)

--- a/IlmCtl/CtlInterpreter.cpp
+++ b/IlmCtl/CtlInterpreter.cpp
@@ -64,6 +64,7 @@
 #include <fstream>
 #include <algorithm>
 #include <cassert>
+#include <unistd.h>
 
 #ifdef WIN32
     #include <io.h>