Gentoo-specific workaround due to https://bugs.gentoo.org/383179
--- a/zip/zunzip.h
+++ b/zip/zunzip.h
@@ -48,4 +48,8 @@
 #include <zlib.h>
 
+#ifndef OF
+#define OF _Z_OF
+#endif
+
 #if defined(STRICTUNZIP) || defined(STRICTZIPUNZIP)
 /* like the STRICT of WIN32, we define a pointer that cannot be converted