Adds a test that errors reported in the inlinable function bodies of
.swiftinterface files are propagated correctly when generating the corresponding
.swiftmodule files.
rdar://problem/44400260
Ensure that we explicitly provide the path to the interpreter when
running the python scripts during the tests. This is needed to have the
tests work on Windows which does not honour the shebang in the file. It
also ensures that we use the correct interpreter for the tests.
