This was reverted due to some failures on specific darwin buildbots,
the issue being that the new lit configuration was not setting the
SDKROOT environment variable.  We've tested a fix locally and confirmed
that it works, so this patch resubmits everything with the fix
applied.

llvm-svn: 318435

This reverts the aforementioned patch and 2 subsequent follow-ups,
as some buildbots are still failing 2 tests because of it.
Investigation is ongoing into the cause of the failures.

llvm-svn: 318112

Previously, debuginfo-tests was expected to be checked out into
clang/test and then the tests would automatically run as part of
check-clang.  This is not a standard workflow for handling
external projects, and it brings with it some serious drawbacks
such as the inability to depend on things other than clang, which
we will need going forward.

The goal of this patch is to migrate towards a more standard
workflow.  To ease the transition for build bot maintainers,
this patch tries not to break the existing workflow, but instead
simply deprecate it to give maintainers a chance to update
the build infrastructure.

Differential Revision: https://reviews.llvm.org/D39605

llvm-svn: 317925