Dump the minimal version of cmake 3.5.0

[sylvestre.ledru]

Summary

This is done to mitigate a build issue with lldb specific to CMake 3.4.*

This won't be a major issue on old distro (Debian jessie or Ubuntu Trusty) as CMake 3.4 isn't available on these distros.

CMake Error at tools/lldb/unittests/tools/lldb-mi/utils/CMakeLists.txt:12 (target_sources):
  Error evaluating generator expression:

    $<TARGET_OBJECTS:lldb-mi-utils>

  The evaluation of the TARGET_OBJECTS generator expression is only suitable
  for consumption by CMake.  It is not suitable for writing out elsewhere.

Version 3.5 has been released 2016-04-15
While 3.4: 2016-01-25

[sgraenitz]

Can you please explain in more detail how this is supposed to fix the issue?

• The 3.4 docs state an example that is very close to what I found in lldb/unittests/tools/lldb-mi/utils/CMakeLists.txt: https://cmake.org/cmake/help/v3.4/command/add_library.html#object-libraries
• Someone with 3.5 that complains about the same issue: https://cmake.org/pipermail/cmake/2016-June/063749.html

We should certainly go to a newer CMake version soon, but I think it needs some more coordination (with other subprojects/LLVM) and it could be a bigger step forward once we do this.

[sylvestre.ledru]

I didn't look at the details. It was failing with 3.4, upgrading to 3.5 address the issue.

To me, this isn't a big deal as both 3.4 and 3.5 are old enough that modern distro have both of them (or none). See:

http://lists.llvm.org/pipermail/llvm-dev/2016-April/098780.html

[sgraenitz]

Ok, so far this appears to be a rare issue that we don't know much about. I think keeping LLVM and its subprojects in sync (which means CMake version 3.4.3) should be the prio for now.

[sylvestre.ledru]

As you wish.
People who might encounter the same issue will (hopefully) find this review

[tatyana-krasnukha]

There is a workaround D63544 for fixing the issue in lldb/unittests/tools/lldb-mi/utils/CMakeLists.txt without changing the minimum required cmake's version.

CMakeLists.txt

 # See docs/CMake.html for instructions about how to build LLVM with CMake.
 
-cmake_minimum_required(VERSION 3.4.3)
+cmake_minimum_required(VERSION 3.5.0)
 
 if(POLICY CMP0068)
   cmake_policy(SET CMP0068 NEW)
   set(CMAKE_BUILD_WITH_INSTALL_NAME_DIR ON)
 endif()
 
 if(POLICY CMP0075)
   cmake_policy(SET CMP0075 NEW)

docs/CMake.rst

 .. _Quick start:
 
 Quick start
 ===========
 
 We use here the command-line, non-interactive CMake interface.
 
 #. `Download <http://www.cmake.org/cmake/resources/software.html>`_ and install
-   CMake. Version 3.4.3 is the minimum required.
+   CMake. Version 3.5.0 is the minimum required.
 
 #. Open a shell. Your development tools must be reachable from this shell
    through the PATH environment variable.
 
 #. Create a build directory. Building LLVM in the source
    directory is not supported. cd to this directory:
 
    .. code-block:: console

 now reliably use CMake to develop their own LLVM-based projects against an
 installed version of LLVM regardless of how it was built.
 
 Here is a simple example of a CMakeLists.txt file that imports the LLVM libraries
 and uses them to build a simple application ``simple-tool``.
 
 .. code-block:: cmake
 
-  cmake_minimum_required(VERSION 3.4.3)
+  cmake_minimum_required(VERSION 3.5.0)
   project(SimpleProject)
 
   find_package(LLVM REQUIRED CONFIG)
 
   message(STATUS "Found LLVM ${LLVM_PACKAGE_VERSION}")
   message(STATUS "Using LLVMConfig.cmake in: ${LLVM_DIR}")
 
   # Set your project compile flags.

docs/CMakePrimer.rst

 ============
 
 The LLVM project and many of the core projects built on LLVM build using CMake.
 This document aims to provide a brief overview of CMake for developers modifying
 LLVM projects or building their own projects on top of LLVM.
 
 The official CMake language references is available in the cmake-language
 manpage and `cmake-language online documentation
-<https://cmake.org/cmake/help/v3.4/manual/cmake-language.7.html>`_.
+<https://cmake.org/cmake/help/v3.5/manual/cmake-language.7.html>`_.
 
 10,000 ft View
 ==============
 
 CMake is a tool that reads script files in its own language that describe how a
 software project builds. As CMake evaluates the scripts it constructs an
 internal representation of the software project. Once the scripts have been
 fully processed, if there are no errors, CMake will generate build files to

 scripting language, but there are a few quirks because, as with everything in
 CMake, control flow constructs are commands.
 
 If, ElseIf, Else
 ----------------
 
 .. note::
   For the full documentation on the CMake if command go
-  `here <https://cmake.org/cmake/help/v3.4/command/if.html>`_. That resource is
+  `here <https://cmake.org/cmake/help/v3.5/command/if.html>`_. That resource is
   far more complete.
 
 In general CMake if blocks work the way you'd expect:
 
 .. code-block:: cmake
 
   if(<condition>)
     message("do stuff")

 all trailing arguments.
 
 CMake provides a module ``CMakeParseArguments`` which provides an implementation
 of advanced argument parsing. We use this all over LLVM, and it is recommended
 for any function that has complex argument-based behaviors or optional
 arguments. CMake's official documentation for the module is in the
 ``cmake-modules`` manpage, and is also available at the
 `cmake-modules online documentation
-<https://cmake.org/cmake/help/v3.4/module/CMakeParseArguments.html>`_.
+<https://cmake.org/cmake/help/v3.5/module/CMakeParseArguments.html>`_.
 
 .. note::
   As of CMake 3.5 the cmake_parse_arguments command has become a native command
   and the CMakeParseArguments module is empty and only left around for
   compatibility.
 
 Functions Vs Macros
 -------------------

 
 Useful Built-in Commands
 ========================
 
 CMake has a bunch of useful built-in commands. This document isn't going to
 go into details about them because The CMake project has excellent
 documentation. To highlight a few useful functions see:
 
-* `add_custom_command <https://cmake.org/cmake/help/v3.4/command/add_custom_command.html>`_
-* `add_custom_target <https://cmake.org/cmake/help/v3.4/command/add_custom_target.html>`_
-* `file <https://cmake.org/cmake/help/v3.4/command/file.html>`_
-* `list <https://cmake.org/cmake/help/v3.4/command/list.html>`_
-* `math <https://cmake.org/cmake/help/v3.4/command/math.html>`_
-* `string <https://cmake.org/cmake/help/v3.4/command/string.html>`_
+* `add_custom_command <https://cmake.org/cmake/help/v3.5/command/add_custom_command.html>`_
+* `add_custom_target <https://cmake.org/cmake/help/v3.5/command/add_custom_target.html>`_
+* `file <https://cmake.org/cmake/help/v3.5/command/file.html>`_
+* `list <https://cmake.org/cmake/help/v3.5/command/list.html>`_
+* `math <https://cmake.org/cmake/help/v3.5/command/math.html>`_
+* `string <https://cmake.org/cmake/help/v3.5/command/string.html>`_
 
 The full documentation for CMake commands is in the ``cmake-commands`` manpage
-and available on `CMake's website <https://cmake.org/cmake/help/v3.4/manual/cmake-commands.7.html>`_
+and available on `CMake's website <https://cmake.org/cmake/help/v3.5/manual/cmake-commands.7.html>`_

docs/ReleaseNotes.rst

.. NOTE
    functionality, or simply have a lot to talk about), see the `NOTE` below
    for adding a new subsection.
 
 * The optimizer will now convert calls to memcmp into a calls to bcmp in some
   circumstances. Users who are building freestanding code (not depending on the
   platform's libc) without specifying -ffreestanding may need to either pass
   -fno-builtin-bcmp, or provide a bcmp function.
 
+* CMake minimal version is now 3.5.0
+
 .. NOTE
    If you would like to document a larger change, then you can add a
    subsection about it right here. You can copy the following boilerplate
    and un-indent it (the indentation causes it to be inside this comment).
 
    Special New Feature
    -------------------
 

runtimes/CMakeLists.txt

 # If this file is acting as a top-level CMake invocation, this code path is
 # triggered by the external project call for the runtimes target below.
 if(${CMAKE_SOURCE_DIR} STREQUAL ${CMAKE_CURRENT_SOURCE_DIR})
 
   function(runtime_register_component name)
     set_property(GLOBAL APPEND PROPERTY SUB_COMPONENTS ${name})
   endfunction()
 
-  cmake_minimum_required(VERSION 3.4.3)
+  cmake_minimum_required(VERSION 3.5.0)
   project(Runtimes C CXX ASM)
 
   # Add the root project's CMake modules, and the LLVM build's modules to the
   # CMake module path.
   list(INSERT CMAKE_MODULE_PATH 0
     "${CMAKE_CURRENT_SOURCE_DIR}/../cmake"
     "${CMAKE_CURRENT_SOURCE_DIR}/../cmake/modules"
     "${LLVM_LIBRARY_DIR}/cmake/llvm"