rexec: hide unnecessary symbols

src/lxc/rexec.h

@@ -3,6 +3,8 @@
 #ifndef __LXC_REXEC_H
 #define __LXC_REXEC_H
 
-extern int lxc_rexec(const char *memfd_name);
+#include "compiler.h"
+
+__hidden extern int lxc_rexec(const char *memfd_name);
 
 #endif /* __LXC_REXEC_H */