Most tests were using %swift or similar substitutions, which did not
include the target triple and SDK. The driver was defaulting to the
host OS. Thus, we could not run the tests when the standard library was
not built for OS X.
Swift SVN r24504
Instead of referencing them by name, serialize a reference to their
storage decl instead, then note which accessor to retrieve.
Uncovered by Chris's override work in r15051...thanks, Chris!
Swift SVN r15063
