spl/lua: restore noreturn annotations

Objtool correctly complains that `spl_panic()` and `luaD_throw()`
are missing an `atribute((noreturn))` annotation. They were in
place but removed in a previous commit to work around spurious
objtool warnings they caused.

Add them back in, the spurious warnings are addressed in a separate
commit.

Signed-off-by: Attila Fülöp <attila@fueloep.org>

Author: AttilaFueloep

include/os/linux/spl/sys/debug.h

@@ -69,19 +69,7 @@
 #define	__maybe_unused __attribute__((unused))
 #endif
 
-/*
- * Without this, we see warnings from objtool during normal Linux builds when
- * the kernel is built with CONFIG_STACK_VALIDATION=y:
- *
- * warning: objtool: tsd_create() falls through to next function __list_add()
- * warning: objtool: .text: unexpected end of section
- *
- * Until the toolchain stops doing this, we must only define this attribute on
- * spl_panic() when doing static analysis.
- */
-#if defined(__COVERITY__) || defined(__clang_analyzer__)
 __attribute__((__noreturn__))
-#endif
 extern void spl_panic(const char *file, const char *func, int line,
     const char *fmt, ...);
 extern void spl_dumpstack(void);

module/lua/llimits.h

@@ -97,10 +97,8 @@ typedef LUAI_UACNUMBER l_uacNumber;
 
 /*
 ** non-return type
-**
-** Suppress noreturn attribute in kernel builds to avoid objtool check warnings
 */
-#if defined(__GNUC__) && !defined(_KERNEL)
+#if defined(__GNUC__) || defined(__clang__) /* XXX separate change? test! */
 #define l_noret		void __attribute__((noreturn))
 #elif defined(_MSC_VER)
 #define l_noret		void __declspec(noreturn)

module/os/linux/spl/spl-err.c

@@ -45,6 +45,7 @@ spl_dumpstack(void)
 }
 EXPORT_SYMBOL(spl_dumpstack);
 
+__attribute__((__noreturn__))
 void
 spl_panic(const char *file, const char *func, int line, const char *fmt, ...)
 {