Update stdlib/macos CI

[MBkkt]

Bug description

Expected behavior

We can use most C++17 (and C++20) features.
But very common C++17 feature: std::from_chars for double not available

Actual behavior

We're using apple libc++, it's outdated.

https://github.com/facebookincubator/velox/actions/runs/18444778495/job/52549931371?pr=15134

In file included from /Users/runner/work/velox/velox/velox/functions/prestosql/registration/DateTimeFunctionsRegistration.cpp:18:
/Users/runner/work/velox/velox/./velox/functions/prestosql/DateTimeFunctions.h:1811:23: error: call to deleted function 'from_chars'
 1811 |     auto [_, error] = std::from_chars(
      |                       ^~~~~~~~~~~~~~~
/Applications/Xcode_16.4.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/c++/v1/__charconv/from_chars_integral.h:38:19: note: candidate function has been explicitly deleted
   38 | from_chars_result from_chars(const char*, const char*, bool, int = 10) = delete;
      |                   ^
/Applications/Xcode_16.4.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/c++/v1/__charconv/from_chars_integral.h:224:1: note: candidate template ignored: requirement 'is_integral<double>::value' was not satisfied [with _Tp = double]
  224 | from_chars(const char* __first, const char* __last, _Tp& __value) {
      | ^
/Applications/Xcode_16.4.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/c++/v1/__charconv/from_chars_integral.h:230:1: note: candidate function template not viable: requires 4 arguments, but 3 were provided
  230 | from_chars(const char* __first, const char* __last, _Tp& __value, int __base) {
      | ^          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

How to fix this?

Ideally use llvm clang and llvm libc++21
It's available for macos15: https://formulae.brew.sh/formula/llvm

Alternatively we can use gnu libstdc++ which is also available on macos

System information

CI

Relevant logs

[MBkkt]

CC @assignUser @kgpai

[assignUser]

wow, that took long to implement... https://libcxx.llvm.org/Status/Cxx17.html#note-p0067

I see you fixed the issue in your pr by using fast_float (which might also be better performance wise? No idea if this is relevant for the context it's used in) so this is not pressing.

We will update to clang 20+ soon anyway for Sanitizers #15130

[MBkkt]

which might also be better performance wise?

for llvm libc++ algorithm is same, not sure about perf.

for gnu libstdc++ they are adopted fast_float code, so also should be same perf

wow, that took long to implement...

As far as I know they just decided to don't do this for some reason.
Then guys from llvm libc implemented this fast_float like algorithm for their usecase.

And the cool part about this, llvm libc++ can reuse headers from llvm libc.
So they finally added this.

llvm/llvm-project#91651