fold strlen after strcmp(a, b) == 0

[GCC bug link](https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92112)
[Clang 22.0 godbolt](https://godbolt.org/z/fWx66xdW3)

Compiling this C code with -O2 does not transform f () and g () to ret void:
```
extern char a[], b[];

void f (void)
{
if (__builtin_strcmp (a, b) != 0)
return;

if (__builtin_strlen (a) != __builtin_strlen (b)) // can be folded to false
__builtin_abort ();
}

void g (void)
{
if (__builtin_strlen (a) < 7)
return;
if (__builtin_strcmp (a, b) != 0)
return;

if (__builtin_strlen (b) < 7) // can be folded to false
__builtin_abort ();
}
```