[docs] Add cmake to Software requirements

[rovka]

Summary

Add cmake to the list of packages required for compiling LLVM.
Also move make to the bottom of the list and mark it as optional.

[sgraenitz]

Yes, agree! Hopefully we will move on to a newer version (3.9?) some time soon, but that needs a broader discussion first.

[thakis]

This broke the sphinx bot:

http://lab.llvm.org:8011/builders/llvm-sphinx-docs/builds/33901/steps/docs-llvm-html/logs/stdio

Warning, treated as error:
/home/buildbot/llvm-build-dir/llvm-sphinx-docs/llvm/src/docs/GettingStarted.rst:3: WARNING: Duplicate explicit target name: "cmake".

Can you take a look?

[sgraenitz]

In D65438#1608900, @thakis wrote:

This broke the sphinx bot

Interesting. Thanks for pointing it out. However, note that it's more like "failing for a different reason" now :)
http://lab.llvm.org:8011/builders/llvm-sphinx-docs/builds/33900/steps/docs-llvm-html/logs/stdio

llvm/trunk/docs/GettingStarted.rst

98

Is this the other "explicit target name"?

[thakis]

Yup, the other one's at https://reviews.llvm.org/D65164#1608898 , that one has a fix committed by now

[thakis]

In D65438#1608900, @thakis wrote:

This broke the sphinx bot:

http://lab.llvm.org:8011/builders/llvm-sphinx-docs/builds/33901/steps/docs-llvm-html/logs/stdio

Warning, treated as error:
/home/buildbot/llvm-build-dir/llvm-sphinx-docs/llvm/src/docs/GettingStarted.rst:3: WARNING: Duplicate explicit target name: "cmake".

Can you take a look?

Ping, this is still broken 5 days later.

[rupprecht]

Did you run ninja docs-llvm-html (or equivalent if not using ninja) when submitting? I'm still seeing this error in trunk.

llvm/trunk/docs/GettingStarted.rst

* Run your build tool of choice!
      * CMake will generate build targets for each tool and library, and most
        LLVM sub-projects generate their own ``check-<project>`` target.
 
      * Running a serial build will be *slow*.  Make sure you run a parallel
        build. That's already done by default in Ninja; for ``make``, use
        ``make -j NNN`` (with an appropriate value of NNN, e.g. number of CPUs
        you have.)
 
    * For more information see `CMake <CMake.html>`_
 
    * If you get an "internal compiler error (ICE)" or test failures, see
      `below`_.
 
 Consult the `Getting Started with LLVM`_ section for detailed information on
 configuring and compiling LLVM.  Go to `Directory Layout`_ to learn about the
 layout of the source code tree.
 

 table below lists those required packages. The Package column is the usual name
 for the software package that LLVM depends on. The Version column provides
 "known to work" versions of the package. The Notes column describes how LLVM
 uses the package and provides other details.
 
 =========================================================== ============ ==========================================
 Package                                                     Version      Notes
 =========================================================== ============ ==========================================
-`GNU Make <http://savannah.gnu.org/projects/make>`_         3.79, 3.79.1 Makefile/build processor
+`CMake <http://cmake.org/>`_                                >=3.4.3      Makefile/workspace generator
 `GCC <http://gcc.gnu.org/>`_                                >=5.1.0      C/C++ compiler\ :sup:`1`
 `python <http://www.python.org/>`_                          >=2.7        Automated test suite\ :sup:`2`
 `zlib <http://zlib.net>`_                                   >=1.2.3.4    Compression library\ :sup:`3`
+`GNU Make <http://savannah.gnu.org/projects/make>`_         3.79, 3.79.1 Makefile/build processor\ :sup:`4`
 =========================================================== ============ ==========================================
 
 .. note::
 
    #. Only the C and C++ languages are needed so there's no need to build the
       other languages for LLVM's purposes. See `below` for specific version
       info.
    #. Only needed if you want to run the automated test suite in the
       ``llvm/test`` directory.
    #. Optional, adds compression / uncompression capabilities to selected LLVM
       tools.
+   #. Optional, you can use any other build tool supported by CMake.
 
 Additionally, your compilation host is expected to have the usual plethora of
 Unix utilities. Specifically:
 
 * **ar** --- archive library builder
 * **bzip2** --- bzip2 command for distribution generation
 * **bunzip2** --- bunzip2 command for distribution checking
 * **chmod** --- change permissions on a file