[Bug rtl-optimization/123517] [16 regression] infinite loop in ext-dce while compiling _gcov_execl.i

[sjames at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123517

--- Comment #3 from Sam James <sjames at gcc dot gnu.org> ---
stage1 is fine:
`/var/tmp/portage/sys-devel/gcc-16.0.9999/work/build/./prev-gcc/xgcc
-B/var/tmp/portage/sys-devel/gcc-16.0.9999/work/build/./prev-gcc/
./_gcov_execl.i -c -m32 -O3 -march=x86-64-v2`

Reduced hanging input:
```
int a;

void foo() {
  __builtin_va_list ap;
  while (__builtin_va_arg(ap, char *))
    ;
  if (a)
    foo();
}
```

Will try revert of lra commit first