properly normalize / validate abiflags and include in environment signature

[davidhewitt]

maturin currently generates PYO3_ENVIRONMENT_SIGNATURE without accounting for abiflags. This in particular means that builds switching between regular and free-threaded Python can fail to invalidate pyo3-ffi's cache and lead to compilation selecting the wrong ABI.

This PR corrects the generated environment signature, and attempts to make abiflag handling correct throughout maturin. In particular I found the following other deficiencies:

• Parsing PYO3_CONFIG_FILE did not infer (or validate) missing ABI flags from Py_GIL_DISABLED or Py_DEBUG.
• The default CPython extension suffix generated from PYO3_CONFIG_FILE omitted free-threaded and debug flags. (This would produce a wheel with an invalid extension for the free-threaded/debug interpreter.)
• Cross-compilation sysconfig parsing did not infer missing ABI flags from build settings.
• Interpreter discovery generally did not account for the possibility of the d debug abiflag.

[messense]

should we also update here?

maturin/src/cross_compile.rs

Lines 65 to 74 in faad068

	print("version_major", build_time_vars["VERSION"][0]) # 3
	print("version_minor", build_time_vars["VERSION"][2:]) # E.g., 8, 10
	KEYS = [
	"ABIFLAGS",
	"EXT_SUFFIX",
	"SOABI",
	"Py_GIL_DISABLED",
	]
	for key in KEYS:
	print(key, build_time_vars.get(key, ""))

[davidhewitt]

Thanks, addressed both points. To keep the ordering consistent I simplified to either generate abiflags matching packaging if no flags present, otherwise I just validate the user-supplied flags at least match the sysconfigdata keys.

[davidhewitt]

conda bug looks possibly unrelated?