[gn build] Add build files for DebugInfo/{DWARF,PDB}, Option,...

[gn build] Add build files for DebugInfo/{DWARF,PDB}, Option, ToolDrivers/llvm-lib, and WindowsManifest

The diff in targets.gni is due to me running `gn format` on all .gn and .gni
files.

llvm_enable_dia_sdk is in a gni file because I'm going to have to read it when
writing the lit invocations for check-llvm and check-lld. I've never had the
DIA sdk installed locally so I never tested building with it enabled -- it
probably doesn't Just Work and needs some path to diaguids.lib. We can finish
that once somebody needs it.

Differential Revision: https://reviews.llvm.org/D55591

llvm-svn: 348908