[libcxx] r243503 - [libcxx] Cleanup CMake configuration and integrate with LLVM

[Eric Fiselier]

FYI I recommitted the working parts of this patch as r243698.  Please
let me know if anything comes up.

/Eric

On Wed, Jul 29, 2015 at 2:33 PM, Hans Wennborg <hans at chromium.org> wrote:
> I've reverted this in r243550 as it caused PR24306.
>
> On Tue, Jul 28, 2015 at 5:03 PM, Eric Fiselier <eric at efcs.ca> wrote:
>> Author: ericwf
>> Date: Tue Jul 28 19:03:51 2015
>> New Revision: 243503
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=243503&view=rev
>> Log:
>> [libcxx] Cleanup CMake configuration and integrate with LLVM
>>
>> Summary:
>> This patch contains the following changes:
>>
>> 1. Require that libc++ can find a LLVM source directory. This is done the same way as `libc++abi` currently does.
>> 2. Cleanup ugly configuration code in CMakeLists.txt by using `add_flags`, `add_flags_if`, and `add_flags_if_supported` macros.
>>
>> The goals for this patch are:
>>
>> 1. Help libc++ be more consistent with how LLVM handles CMake options (see PR23670 PR23671).
>> 2. Make it easier to use sanitizers using the `LLVM_USE_SANITIZER` option.
>> 3. Make libc++'s CMakeLists.txt file easier to understand and change.
>> 4. Move towards allowing libc++ to create Sphinx documentation (see http://efcs.ca/libcxx-docs).
>> 5. Move towards allowing  libc++ to use other LLVM utilities such as `not` and `FileCheck`.
>>
>>
>>
>> Reviewers: mclow.lists, jroelofs, danalbert
>>
>> Subscribers: cfe-commits
>>
>> Differential Revision: http://reviews.llvm.org/D11308