Use _Noreturn (C11; GNU89) properly

A function that returns with no value is a different thing from a
function that doesn't return at all.  Those are two orthogonal
concepts, commonly confused.

pthread_create(3) expects a pointer to a start routine that has a
very precise prototype:

    void *(*start_routine)(void *);

However, other thread functions, such as kernel ones, expect:

    void (*start_routine)(void *);

Providing a different one is incorrect, and has only been working
because the ABIs happen to produce a compatible function.

We should use '_Noreturn void', since it's the natural type, and
then provide a '_Noreturn void *' wrapper for pthread functions.

For consistency, replace most cases of __NORETURN or
__attribute__((noreturn)) by _Noreturn.  _Noreturn is understood
by -std=gnu89, so it should be safe to use everywhere.

Ref: https://github.com/openzfs/zfs/pull/13110#discussion_r808450136
Ref: https://software.codidact.com/posts/285972
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Co-authored-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Closes #13120

module/lua/ldo.c

@@ -91,7 +91,7 @@ static intptr_t stack_remaining(void) {
 typedef	struct _label_t { long long unsigned val[JMP_BUF_CNT]; } label_t;
 
 int setjmp(label_t *) __attribute__ ((__nothrow__));
-extern void longjmp(label_t *) __attribute__((__noreturn__));
+extern _Noreturn void longjmp(label_t *);
 
 #define LUAI_THROW(L,c)		longjmp(&(c)->b)
 #define LUAI_TRY(L,c,a)		if (setjmp(&(c)->b) == 0) { a }