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
This takes all %target-run-simple-swift and %target-run-stdlib-swift
invocations and runs them using the interpreter instead. To enable this
mode, pass --param=interpret to lit.py; you can add this flag to the
LLVM_LIT_ARGS CMake setting (which defaults to "-sv").
This doesn't support separated %target-build / %target-run steps, nor
does it work with StdlibUnittest (which uses posix_spawn to run its
subtasks). But it's a start.
<rdar://problem/17938202>
Swift SVN r21391
