[PATCH] Allow CMake to build Sphinx documentation

[Dan Liew]

> This is looking really good. I would like to remove the linkcheck target
> just on the principle that the build should not go accessing external
> websites.

Sure. I feel as if users should still be made aware of this feature (I
certainly didn't know about it before I started this work).

Would it be okay to add information about how to check links manually
to http://llvm.org/docs/SphinxQuickstartTemplate.html as a separate
patch?

Since I'm going to rework the patch again I'd like to ask people's
opinions on a few things before I start

- Are the names of the targets okay?

* docs-llvm-html
* docs-llvm-man

i.e. if you build with LLVM_ENABLE_SPHINX you can type ``make
docs-llvm-html`` and ``make docs-llvm-man`` to build documentation.

- I've assumed the add_sphinx_target() function is reusable by other
projects like Clang and lldb. This might not be the case depending on
how these projects interact with LLVM's CMake build system. I've only
ever built Clang inside the LLVM tree (a case where reusing
add_sphinx_target should work) but I'm sure I remember reading
somewhere that Clang can be built out of tree and in that case I have
doubts about reusing add_sphinx_target() working. I've never even
built lldb but the instructions seem to say I should build in tree.

 Would it be worth trying to apply the add_sphinx_target() functin to
Clang and lldb as well?


> You should send 0002 in a separate patch thread. I don't really have the
> knowledge to sign off on it. I think you'll want to CC chapuni or chandler.

Sure I'll do that.

Thanks,
-- 
Dan Liew
PhD Student - Imperial College London