only define safe_fork() in systems with linux namespaces

src/system.c

@@ -67,7 +67,7 @@ pid_t safe_fork(void)
 		return -1;
 	return ret;
 #else
-	return fork();
+	return -1;
 #endif
 }
 

src/system.h

@@ -36,7 +36,12 @@ typedef void (*sighandler_t)(int);
 # define SIGHANDLER_T sighandler_t
 #endif
 
+#if defined(__linux__) && defined(ENABLE_LINUX_NS)
 pid_t safe_fork(void);
+#else
+# define safe_fork fork
+#endif
+
 void pr_set_undumpable(const char* mod);
 void kill_on_parent_kill(int sig);