[Bug target/102953] Improvements to CET-IBT and ENDBR generation

["hjl.tools at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102953

--- Comment #10 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to Andrew Cooper from comment #8)
> Actually, there is a (possibly pre-existing) diagnostics issue:
> 
> $ cat proto.c
> static void __attribute__((cf_check)) foo(void);
> static void __attribute__((unused)) foo(void)
> {
> }
> void (*ptr)(void) = foo;
> 
> $ gcc -Wall -Os -fcf-protection=branch -mmanual-endbr
> -fcf-check-attribute=no -c proto.c -o proto.o
> proto.c:2:37: error: conflicting types for 'foo'; have 'void(void)'
>     2 | static void __attribute__((unused)) foo(void)
>       |                                     ^~~
> proto.c:1:39: note: previous declaration of 'foo' with type 'void(void)'
>     1 | static void __attribute__((cf_check)) foo(void);
>       |                                       ^~~
> 
> 
> The diagnostic complaining that the forward declaration doesn't match the
> definition gives 'void(void)' as the type in both cases, leaving out the
> fact that they differ by cf_check-ness.

Please try the v2 patch.