Don't check target architecture if cross-compiling

[dalcde]

Part of the point of cross-compiling is to be able to compile to other architectures.

This is needed in order to compile to wasm32-unknown-unknown: see #1221

[davidhewitt]

I'm wary of this... The purpose of check_target_architecture is to give a friendly error message at build time if the Rust target doesn't match what PyO3 has detected from the config.

If it's wrong for you, this could mean that the library you're getting build configuration from thinks the pointer size is 64-bit?

If your build configuration really is correct, I think rather than disable this check for all cross compiles I'd rather have an environment variable PYO3_ALLOW_INCORRECT_ARCHITECTURE (or a better name if you can think of one). So that in cases like this, users who know what they're doing can proceed anyway.

[davidhewitt]

... maybe PYO3_SKIP_TARGET_CHECK is a better name for the environment variable.

[dalcde]

Ah I think I misunderstood the purpose of this code. It correctly identified that I previously had a broken _sysconfigdata_*.py and threw an error. The problem is now fixed in upstream pyodide.