GCC (as of 15.2.1_p20260214) seems to fail, specifically for GNU Hurd (as seen
by the !defined (__linux__) bit), as gcc's __attribute__ expects an argument
there. It seems rather old (and quite undesirable), so for now, we will just
disable the snippet of code.

diff '--color=auto' -ru NetHack-3.6.7/include/tradstdc.h NetHack-3.6.7-fix/include/tradstdc.h
--- NetHack-3.6.7/include/tradstdc.h	2023-02-15 16:52:57.000000000 -0500
+++ NetHack-3.6.7-fix/include/tradstdc.h	2026-03-24 00:48:35.740547092 -0400
@@ -429,7 +429,7 @@
 #if __GNUC__ >= 3
 #define UNUSED __attribute__((unused))
 #define NORETURN __attribute__((noreturn))
-#if !defined(__linux__) || defined(GCC_URWARN)
+#if 0
 /* disable gcc's __attribute__((__warn_unused_result__)) since explicitly
    discarding the result by casting to (void) is not accepted as a 'use' */
 #define __warn_unused_result__ /*empty*/