gh-127432: Add CI job to cross build Python

[matthewhughes934]

This is to avoid regressions in the cross building process

• Issue: Add CI test for cross-builds #127432

[matthewhughes934]

There was a failure when I was using a relative path for the prefix with a9d74a4, error output https://productionresultssa9.blob.core.windows.net/actions-results/f1a2624a-3f06-4952-a7e9-b07f4b8f5d8e/workflow-job-run-b9cd78bf-63c7-5764-7bde-3692ae1765e4/logs/job/job-logs.txt?rsct=text%2Fplain&se=2024-12-31T18%3A50%3A34Z&sig=VmOEHKOZajRQ6siRvIW1zZMd0%2BPqBhuELzZLqiitlxY%3D&ske=2025-01-01T03%3A11%3A03Z&skoid=ca7593d4-ee42-46cd-af88-8b886a2f84eb&sks=b&skt=2024-12-31T15%3A11%3A03Z&sktid=398a6654-997b-47e9-b12b-9515b896b4de&skv=2024-11-04&sp=r&spr=https&sr=b&st=2024-12-31T18%3A40%3A29Z&sv=2024-11-04, relative bit:

2024-12-31T18:12:42.0721807Z test test_sysconfig failed -- Traceback (most recent call last):
2024-12-31T18:12:42.0723114Z   File "/home/runner/work/cpython/build/cross-python/lib/python3.14/test/test_sysconfig.py", line 658, in test_sysconfigdata_json
2024-12-31T18:12:42.0724161Z     self.assertEqual(system_config_vars, json_config_vars)
<-- SNIP -->
2024-12-31T18:12:42.1067972Z -  'base': '/home/runner/work/cpython/build/cross-python',
2024-12-31T18:12:42.1068211Z +  'base': '/home/runner/work/cpython/cpython/../build/cross-python',
2024-12-31T18:12:42.1068292Z ?                                     +++++++++++
2024-12-31T18:12:42.1068298Z 
2024-12-31T18:12:42.1068501Z    'datarootdir': '/home/runner/work/cpython/cpython/../build/cross-python/share',
2024-12-31T18:12:42.1068643Z -  'exec_prefix': '/home/runner/work/cpython/build/cross-python',
2024-12-31T18:12:42.1068812Z +  'exec_prefix': '/home/runner/work/cpython/cpython/../build/cross-python',
2024-12-31T18:12:42.1068959Z ?                                            +++++++++++
2024-12-31T18:12:42.1068963Z 
2024-12-31T18:12:42.1069142Z    'host_exec_prefix': '/home/runner/work/cpython/cpython/../build/cross-python',
2024-12-31T18:12:42.1069312Z    'host_prefix': '/home/runner/work/cpython/cpython/../build/cross-python',
2024-12-31T18:12:42.1069396Z    'implementation': 'Python',
2024-12-31T18:12:42.1069479Z    'implementation_lower': 'python',
2024-12-31T18:12:42.1069636Z -  'installed_base': '/home/runner/work/cpython/build/cross-python',
2024-12-31T18:12:42.1069817Z +  'installed_base': '/home/runner/work/cpython/cpython/../build/cross-python',
2024-12-31T18:12:42.1069900Z ?                                               +++++++++++
2024-12-31T18:12:42.1069904Z 
2024-12-31T18:12:42.1070073Z -  'installed_platbase': '/home/runner/work/cpython/build/cross-python',
2024-12-31T18:12:42.1070264Z +  'installed_platbase': '/home/runner/work/cpython/cpython/../build/cross-python',
2024-12-31T18:12:42.1070347Z ?                                                   +++++++++++
2024-12-31T18:12:42.1070357Z 
2024-12-31T18:12:42.1070493Z -  'platbase': '/home/runner/work/cpython/build/cross-python',
2024-12-31T18:12:42.1070654Z +  'platbase': '/home/runner/work/cpython/cpython/../build/cross-python',
2024-12-31T18:12:42.1070740Z ?                                         +++++++++++
2024-12-31T18:12:42.1070744Z 
2024-12-31T18:12:42.1070817Z    'platlibdir': 'lib',
2024-12-31T18:12:42.1070943Z -  'prefix': '/home/runner/work/cpython/build/cross-python',
2024-12-31T18:12:42.1071229Z +  'prefix': '/home/runner/work/cpython/cpython/../build/cross-python',
2024-12-31T18:12:42.1071314Z ?                                       +++++++++++

I wonder if there should be some parth normalisation done?

[matthewhughes934]

I created b4a9069 to demonstrate this changes would actually catch the regression we expect it to

[hugovk]

I created b4a9069 to demonstrate this changes would actually catch the regression we expect it to

And here's the corresponding CI run: https://github.com/python/cpython/actions/runs/12570786158/job/35040972014

cc @FFY00

[FFY00]

I am gonna update the branch to pull the changes from GH-128558, to make sure it still works.

[FFY00]

@hugovk, I think it would make sense to add this as a required check (all-required-green). Do you think that makes sense, or do have any concerns?

[FFY00]

@matthewhughes934, thank you so much for working on this 😊!

[hugovk]

@hugovk, I think it would make sense to add this as a required check (all-required-green). Do you think that makes sense, or do have any concerns?

Let's continue in #129459 :)