use __dead macro from sys/cdefs.h

include/sys/cdefs.h

@@ -0,0 +1,16 @@
+/*
+ * Public domain
+ * sys/cdefs.h compatibility shim
+ */
+
+#include_next <sys/cdefs.h>
+
+#ifndef LIBCOMPAT_SYS_CDEFS_H
+#define LIBCOMPAT_SYS_CDEFS_H
+
+#if !defined(HAVE_ATTRIBUTE__DEAD) && !defined(__dead)
+#define __dead          __attribute__((__noreturn__))
+#define __pure          __attribute__((__const__))
+#endif
+
+#endif

include/sys/types.h

@@ -14,10 +14,6 @@
 #include <_bsd_types.h>
 #endif
 
-#if !defined(HAVE_ATTRIBUTE__DEAD) && !defined(__dead)
-#define __dead
-#endif
-
 #if !defined(HAVE_ATTRIBUTE__BOUNDED__) && !defined(__bounded__)
 # define __bounded__(x, y, z)
 #endif