[lldb][docs] Update landing page for monorepo

[sgraenitz]

Summary

Following up from D65330, here's an update for the landing page.

[sgraenitz]

@clayborg I added a direct link to Xcode project generation here. Is that fine?

[jryans]

Thanks for working on this! 😁

lldb/docs/index.rst

104 ↗

(On Diff #212311)

At some point, we should clarify that Phabricator is where reviews happen these days, but that's an LLVM-wide issue (see the recent RFC and D63488 hoping to clarify).

Perhaps LLDB can update its own pages independently of that process, but once again, I suppose that's a separate topic and separate patch from this one. 😅

lldb/trunk/docs/index.rst

 * Windows local user-space debugging for i386 (*)
 
 (*) Support for Windows is under active development. Basic functionality is
 expected to work, with functionality improving rapidly.
 
 Get Involved
 ------------
 
-To check out the code, use:
+Check out the LLVM source-tree with git and find the sources in the `lldb`
+subdirectory:
 
-svn co http://llvm.org/svn/llvm-project/lldb/trunk lldb
+::
 
-Note that LLDB generally builds from top-of-trunk
+  > git clone https://github.com/llvm/llvm-project.git
 
-* On macOS with Xcode
-* On Linux and FreeBSD (with clang and libstdc++/libc++)
-* On NetBSD (with GCC and clang and libstdc++/libc++)
-* On Windows with VS 2012 or higher using CMake
+Note that LLDB generally builds from top-of-trunk using CMake and Ninja.
+Additionally it builds:
 
-See the LLDB Build Page for platform-specific build instructions.
+* on macOS with a :ref:`generated Xcode project <CMakeGeneratedXcodeProject>`
+* on Linux and FreeBSD with clang and libstdc++/libc++
+* on NetBSD with GCC/clang and libstdc++/libc++
+* on Windows with a generated project for VS 2017 or higher
+
+See the :doc:`LLDB Build Page <resources/build>` for build instructions.
 
 Discussions about LLDB should go to the `lldb-dev
 <http://lists.llvm.org/mailman/listinfo/lldb-dev>`__ mailing list. Commit
-messages for the lldb SVN module are automatically sent to the `lldb-commits
+messages are automatically sent to the `lldb-commits
 <http://lists.llvm.org/mailman/listinfo/lldb-commits>`__ mailing list , and
 this is also the preferred mailing list for patch submissions.
 
-See the Projects page if you are looking for some interesting areas to
-contribute to lldb.
+See the :doc:`Projects page <status/projects>` if you are looking for some
+interesting areas to contribute to lldb.
 
 .. toctree::
    :hidden:
    :maxdepth: 1
    :caption: Goals & Status
 
    status/goals
    status/features

lldb/trunk/docs/resources/build.rst

::
 
   > cmake -B /path/to/lldb-build -G Ninja \
           -C /path/to/llvm-project/lldb/cmake/caches/Apple-lldb-macOS.cmake \
           -DLLVM_ENABLE_PROJECTS="clang;libcxx;lldb" \
           llvm-project/llvm
 
   > DESTDIR=/path/to/lldb-install ninja -C /path/to/lldb-build check-lldb install-distribution
 
+.. _CMakeGeneratedXcodeProject:
+
 Build LLDB standalone for development with Xcode:
 
 ::
 
   > git clone https://github.com/llvm/llvm-project
 
   > cmake -B /path/to/llvm-build -G Ninja \
           -C /path/to/llvm-project/lldb/cmake/caches/Apple-lldb-base.cmake \