[LLVMdev] [RFC] Raise minimum required CMake version to 3.0

[Rafael Espíndola]

> The biggest problem seems to be a potential increase in the cost of
> package management, which is limited to Ubuntu and RHEL. Debian Jesse
> (to be marked stable *very* soon) will come with 3.0, and Fedora, Arch
> and others are already on it or newer. But LTS users are a large
> number of users.
>
> The refusal is not that strong, I agree, but the concrete benefits,
> which right now is just "a nicer way to fix compiler-rt" also don't
> seem strong enough to counter that weak refusal.

So that we can drop autotools, which currently requires anyone wanting
to change the build to install an old version of autoconf, among other
pains. Having two build systems is a way bigger pain than someone
having to install cmake.

I still don't see why we should *ever* take the package management
into consideration if we are OK at all with asking OS X and Windows
users to manually install something. In my experience the claim that
Linux is a more common for development doesn't hold. I personally use
it on a desktop and OS X on a laptop, but most developers I have seem
have a mix of Windows and OS X.

When the issue was mentioned on the context of OS X, the response was
*very* different:
http://lists.cs.uiuc.edu/pipermail/llvmdev/2013-May/062372.html.

An useful conclusion to this thread would be something like ""we can
switch to cmake 3.0 if a patch to fix pr14109 and/or pr21562 uses
cmake 3.0 features".

Cheers,
Rafael