[PATCH] Add module flags metadata to record the settings for enum and wchar width

[Renato Golin]

> With the current backend implementation, if there is no metadata the build attribute will not be emitted, and the default build attribute is that enums/wchars were not used as this is the only safe default. If the backend were to work out the default, this would duplicate the logic for selecting the default, and if we get it wrong the build attributes will not match the code.

I know, and that was my point. I think we are in agreement as to what the dangers are (regarding dealing with the default and the current implementation, which might not be the same). I haven't gone through all possibilities myself, but I trust you have, so if you're happy with the metadata being applied for every ARM target, I'm happy too.

Though, it'd be best not to do that for any other target, since this is an ARM ABI specific flag.

http://reviews.llvm.org/D4212