[patch] PR debug/66653: avoid late_global_decl on decl_type_context()s

[Aldy Hernandez <aldyh at redhat dot com>]

The problem here is that we are trying to call 
dwarf2out_late_global_decl() on a static variable in a template which 
has a type of TEMPLATE_TYPE_PARM:

template <typename T> class A
{
  static __thread T a;
};

We are calling late_global_decl because we are about to remove the 
unused static from the symbol table:

	  /* See if the debugger can use anything before the DECL
	     passes away.  Perhaps it can notice a DECL that is now a
	     constant and can tag the early DIE with an appropriate
	     attribute.

	     Otherwise, this is the last chance the debug_hooks have
	     at looking at optimized away DECLs, since
	     late_global_decl will subsequently be called from the
	     contents of the now pruned symbol table.  */
	  if (!decl_function_context (node->decl))
	    (*debug_hooks->late_global_decl) (node->decl);

Since gen_type_die_with_usage() cannot handle TEMPLATE_TYPE_PARMs we ICE.

I think we need to avoid calling late_global_decl on DECL's for which 
decl_type_context() is true, similarly to what we do for the call to 
early_global_decl in rest_of_decl_compilation:

      && !decl_function_context (decl)
      && !current_function_decl
      && DECL_SOURCE_LOCATION (decl) != BUILTINS_LOCATION
      && !decl_type_context (decl))
    (*debug_hooks->early_global_decl) (decl);

Presumably the old code did not run into this problem because the 
TEMPLATE_TYPE_PARAMs had been lowered by the time dwarf2out_decl was 
called, but here we are calling late_global_decl relatively early.

The attached patch fixes the problem.

Tested with --enable-languages=all.  Ada had other issues, so I skipped it.

OK for mainline?

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