Darwin systems currently do not support dwarf version 3 or above. When we are
ready, we can bump the default to gdwarf-4 for Darwin.
For other systems, the default is dwarf version 3, if everything goes smoothly,
we can bump the version to 4.
rdar://13591116
llvm-svn: 185483
These options will add a module flag with name "Dwarf Version".
The behavior flag is currently set to Warning, so when two values disagree,
a warning will be emitted.
llvm-svn: 184276