This reverts commits r26369 & r26381.
After upstream clang changes, reverted r25843 which was compensating for a previous upstream clang change.
But keep test/IDE/complete_from_clang_framework.swift disabled for further investigation, because it
seems to have some duplications in a code-completion test.
rdar://20245658&20247922
Swift SVN r26430
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