dwarf2: force_decl_die abort for CONST_DECL

[Graham Stott]

Andrew,

Thanks for rthe pointer to PR 14718

The problem is the new dwarf2out_imported_module_or_decl hook
it's passing a CONST_DECL directly down to force_decl_die.

I'm testing a patch which instead passes CONST_DECL's down
to force_type_die that does fix the aborts, but I've no idea
at present if the resulting dwarf2 info generated is correct.

Guess it's time to do some more digging/testing.

Time to build

Thanks
Graham