ln -r and cherry picking.

[Cary Coutant]

>  2) LTO sections need to be able to find "their index" of decls and
>  types.  By "their index" I mean the index that each section used to
>  reference the decls and types when the section was generated.

Can't you just put an ELF symbol (can be an unnamed local -- could
even just be a section symbol) on the index section, then add a
pointer in the IR section with a relocation to that symbol? This is
basically how DWARF .debug_info sections point to the abbrev table in
the .debug_abbrev sections.

-cary