[PATCH] [lld][core] sectionGroup support.

[Rafael Espíndola]

> Well, the spec still defines some semantics. It seems to me we need to
> pass it through unmodified in -r mode. We also need to make correct
> garbage collection choices. Other than that it doesn't matter. There's
> no special symbol resolution handling.

So, the spec only defines

* GRP_COMDAT
* GRP_MASKOS
* GRP_MASKPROC

COMDAT we can and must handle. Any other bit set will mean a future
version of the standard, an OS or CPU specific group type. I think an
error (other than the -r special case) is the only safe thing to do.
All 3 cases can have special semantics (keep largest, keep the one
from the newest file, whatever). We really cannot guess.

Cheers,
Rafael