[lld][Driver] The driver was creating linker inputs twice

Also add a llvm_unreachable call so that the linker will trip on unhandled
inputElement types.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@189887 91177308-0d34-0410-b5e6-96231b3b80d8
Start a TODO list for the ELF backend.


git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@189890 91177308-0d34-0410-b5e6-96231b3b80d8
[lld][Driver] remove return after llvm_unreachable

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@189891 91177308-0d34-0410-b5e6-96231b3b80d8
Rename *Options.td -> <flavor>Options.td.

Before this patch, name of driver implementation is not consistent with its
option table file. Specifically, LDOptions has a different prefix than
GnuLdDriver.

This patch renames option files, so that the option files have the same prefix
as the corresponding driver files.

Differential Revision: http://llvm-reviews.chandlerc.com/D1591

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@189895 91177308-0d34-0410-b5e6-96231b3b80d8