swift234

[Serialization] Serialize the SDK path and -Xcc arguments for an app.

...so that the debugger has the best possible chance of being able to load
the app properly.

We don't do this for frameworks today because we don't want to leak this
information into the public module; once we have a distinction between
"the module that ships with the framework" and "the module that goes into
the debug info" we can do this for frameworks as well.

Part of rdar://problem/17670778

Swift SVN r25204