swift234

Always emit .d and .swiftdeps files, even if there were errors in the AST.

Yes, they may not be correct, but the stale ones that were there before
won't be correct either (if they were there at all). This should make both
Xcode and the Swift driver less likely to have issues when there's an error
in a newly added file.

Goes with rdar://problem/19640006

Swift SVN r24824