Accept macOS triples in the Apple OS version split

[MementoRC]

crossenv 1.6.1 cannot set up a cross-python for any macOS host. _split_apple_os_version whitelists only ios, tvos and watchos, so every *-apple-darwin* triple reaches the raise:

ERROR: Unknown Apple compiler triple.

The unconditional path is _clean_triple, which calls it for any triple whose vendor is apple, from find_compiler_info's -dumpmachine sanity check. That check is only meant to warn ("We won't overcomplicate this, since it's just to generate a warning"), but the call is not guarded, so the exception aborts setup instead. get_uname_info's host_platform fallback hits the same raise when _PYTHON_HOST_PLATFORM is empty.

1.5.0 had no Apple branching here and was unaffected.

With darwin handled, the rest of the macOS path already works: host_machine comes from the triple's CPU field, host_release from MACOSX_DEPLOYMENT_TARGET, and sysconfig_platform from the existing host_sys_platform == "darwin" branch. The version returned for macOS is the Darwin kernel version and is not read on that path; stripping it also makes the warning comparison correct, since clang reports the running kernel (x86_64-apple-darwin24.6.0) while HOST_GNU_TYPE carries the SDK one (x86_64-apple-darwin13.4.0), and both now reduce to x86_64-apple-darwin.

Seen on conda-forge cross-compiling osx-64 from osx-arm64 with crossenv 1.6.1. There is no macOS lane in CI, so this is not covered by the test matrix.

Adjacent, not touched here: MACOSX_DEPLOYMENT_TARGET majors other than 10 and 11 raise a few lines further down, which would break a 12.0+ target.

[MementoRC]

Passing tests are inconclusive here, no macos lanes

[MementoRC]

@isuruf This just occurred, it felt similar enough to #165 to investigate and PR

[sea-bass]

I just ran into this on conda-forge/toppra-feedstock#19

See e.g.: https://dev.azure.com/conda-forge/feedstock-builds/_build/results?buildId=1588834&view=logs&jobId=899534ae-d486-52b7-7b1c-5c9a77433eb6&j=911cd101-01ff-5c7b-1f72-f391560ba336&t=87cc1423-9314-565b-41af-049b7cc341c6

Looking forward to the fix!

[isuruf]

Wouldn't it be better to do something like

offset = next((i for i, c in enumerate(value) if c.isdigit()), None)

Then we can also allow something like macos too. the triple can be x86_64-apple-macos11.0 sometimes

[MementoRC]

Indeed, a new test accompanies it since the 'no macos lane' comment is irrelevant