analyzer: fix ICE on machine-specific builtins [PR96962]

analyzer: fix ICE on machine-specific builtins [PR96962]

In g:ee7bfbe5eb70a23bbf3a2cedfdcbd2ea1a20c3f2 I added a
  switch (DECL_UNCHECKED_FUNCTION_CODE (callee_fndecl))
to region_model::on_call_pre guarded by
  fndecl_built_in_p (callee_fndecl).
I meant to handle only normal built-ins, whereas this
single-argument overload of fndecl_built_in_p returns true for any
kind of built-in.

PR analyzer/96962 reports a case where this matches for a
machine-specific builtin, leading to an ICE.  Fixed thusly.

gcc/analyzer/ChangeLog:
	PR analyzer/96962
	* region-model.cc (region_model::on_call_pre): Fix guard on switch
	on built-ins to only consider BUILT_IN_NORMAL, rather than other
	kinds of build-ins.