[libcxx-commits] [libcxx] [libc++] Switch FreeBSD CI job to Clang 17 (PR #86320)

[Ed Maste via libcxx-commits]

emaste wrote:

Observed the following failures on the FreeBSD builder with this change:
```
********************
Failed Tests (5):
  llvm-libc++-shared.cfg.in :: libcxx/selftest/modules/std-and-std.compat-module.sh.cpp
  llvm-libc++-shared.cfg.in :: libcxx/selftest/modules/std-module.sh.cpp
  llvm-libc++-shared.cfg.in :: libcxx/selftest/modules/std.compat-module.sh.cpp
  llvm-libc++-shared.cfg.in :: std/modules/std.compat.pass.cpp
  llvm-libc++-shared.cfg.in :: std/modules/std.pass.cpp
```

Typical error:
```
# | In file included from /home/buildkite/.buildkite-agent/builds/freebsd-test-1/llvm-project/libcxx-ci/build/generic-cxx23/modules/c++/v1/std.cppm:227:
# | /home/buildkite/.buildkite-agent/builds/freebsd-test-1/llvm-project/libcxx-ci/build/generic-cxx23/modules/c++/v1/std/cfenv.inc:16:14: error: using declaration referring to 'feclearexcept' with internal linkage cannot be exported
# |    16 |   using std::feclearexcept;
# |       |              ^
# | /usr/include/fenv.h:267:1: note: target of using declaration
# |   267 | feclearexcept(int __excepts)
# |       | ^
```

https://github.com/llvm/llvm-project/pull/86320