[libc++] Remove mention of official support for FreeBSD

[ldionne]

Summary

Libc++'s policy is that we only officially support configurations that
we have CI for. This has been instrumental in providing an implementation
of quality while ensuring low friction for contributors.

We've been making an exception for FreeBSD because it has been supported
for a long time and it's an important platform. However, after requesting
FreeBSD CI for more than a year, it is time to stop making an exception
and hold all platforms to the same standards.

This will be committed after branching for LLVM 15 unless FreeBSD CI is
added before then.

[ldionne]

This discussion came up on Discord, and several contributors (including myself) agreed that we needed to treat all platforms fairly with respect to our CI requirement. I actually hope that I'll never commit this change -- this is basically just a way to officially say "let's now prioritize adding CI for FreeBSD". Doing so is really easy and we will be happy to help out (reaching out on Discord is probably easiest).

[Mordante]

In D127657#3578248, @ldionne wrote:

This discussion came up on Discord, and several contributors (including myself) agreed that we needed to treat all platforms fairly with respect to our CI requirement. I actually hope that I'll never commit this change -- this is basically just a way to officially say "let's now prioritize adding CI for FreeBSD". Doing so is really easy and we will be happy to help out (reaching out on Discord is probably easiest).

+1
It would be really great to have a FreeBSD tested in our CI!

[EricWF]

It's worth noting that buildkite supports FreeBSD, so there shouldn't be any fundamental issues trying to add a builder once we have hardware.

[mstorsjo]

It’s also worth pointing out that being off this list doesn’t mean that code for the platforms is ripped out - there’s many platforms that are supported on a best effort basis.

[emaste]

I actually hope that I'll never commit this change

Thank you - this issue is my fault, I promised but have not yet succeeded in providing a FreeBSD CI instance. I'll prioritize getting this done.

[ldionne]

In D127657#3578949, @emaste wrote:

I actually hope that I'll never commit this change

Thank you - this issue is my fault, I promised but have not yet succeeded in providing a FreeBSD CI instance. I'll prioritize getting this done.

Awesome, thanks! Reach out via discord or e-mail and I'll give you a BuildKite token. You can see the documentation for adding a new CI job here: https://libcxx.llvm.org/AddingNewCIJobs.html#addingnewcijobs

[ldionne]

Abandoning because of D128084. @emaste , can you please still work on providing us with an official FreeBSD builder?

libcxx/docs/index.rst

 ============ =============== ========================== =====================
 
 Libc++ also supports common platforms and architectures:
 
 =============== ========================= ============================
 Target platform Target architecture       Notes
 =============== ========================= ============================
 macOS 10.9+     i386, x86_64, arm64       Building the shared library itself requires targetting macOS 10.11+
-FreeBSD 10+     i386, x86_64, arm
 Linux           i386, x86_64, arm, arm64
 Windows         i386, x86_64              Both MSVC and MinGW style environments
 AIX             powerpc, powerpc64
 =============== ========================= ============================
 
 Generally speaking, libc++ should work on any platform that provides a fairly complete
 C Standard Library. It is also possible to turn off parts of the library for use on
 systems that provide incomplete support.