Enable use of std::format for AppleClang / Xcode 16

[rothmichaels]

Specified the minimum apple-clang version to support std::format to 16 for connanfile.py. Xcode 16 does include the <format> header but does not seem to have the __cpp_lib_format compatibility macro defined so a similar override was needed as we had for Clang 17.

To be able to use std::format with Xcode 16 I had to pass -DMP_UNITS_API_STD_FORMAT=AUTO when calling cmake. Is this expected or is this a sign I missed something in my changes to CMakeLists.txt?

• Wait until Update Xcode versions for apple-clang builds #651 merges and rebase this so we have Xcode 16 CI coverage

[mpusz]

To be able to use std::format with Xcode 16 I had to pass -DMP_UNITS_API_STD_FORMAT=AUTO when calling cmake. Is this expected or is this a sign I missed something in my changes to CMakeLists.txt?

Conan should use std::format by default if supported. You can try to force it from the Conan command line with -o '&:std_format=True' and see what happens.

[rothmichaels]

To be able to use std::format with Xcode 16 I had to pass -DMP_UNITS_API_STD_FORMAT=AUTO when calling cmake. Is this expected or is this a sign I missed something in my changes to CMakeLists.txt?

Conan should use std::format by default if supported. You can try to force it from the Conan command line with -o '&:std_format=True' and see what happens.

Oh, actually this must have been confusion on my part looking at some of my temporary debug messages while I wile I was editing the CMakeList.txt. -DMP_UNITS_API_STD_FORMAT=AUTO is not needed after all.

[mpusz]

generate-job-matrix.py should probably also be updated in line 67. Additionally, could you please also update the table at https://mpusz.github.io/mp-units/latest/getting_started/cpp_compiler_support?

[mpusz]

Thanks!