[PATCH] [lld][ELF] Add linker script ENTRY command

[Michael Spencer]

  The parsing change looks fine, but I'm not sure about maybeSetDefaultOptions.

  I have two issues. The first is that for library use, we want the user to be able to reuse a TargetInfo object without it being changed out from under them. I believe We've already discussed the need to move inputFiles out of TargetInfo for this reason.

  The second is that in link.exe mode some linker options can actually be set while loading object files from archives. So it would have to be run after the resolver, which doesn't really fit the semantics.

  I think the solution here is to make a copy of the TargetInfo object passed to the driver (this can't be done currently due to the _inputFiles member) and pass that around as a non-const reference (no const_cast). Default options can be computed as requested.

http://llvm-reviews.chandlerc.com/D833

BRANCH
  linker-script-entry

ARCANIST PROJECT
  lld