Use manylinux-entrypoint script for linux wheel builds

[ngoldbaum]

See pypa/manylinux#1825 (comment) for an explanation of why we need to use this.

PR'd separately from #12555 per #12555 (comment)

[alex]

This makes sense and seems simple enough. My own question is: how did armv7 ever work without this??? Do you have any idea?

[ngoldbaum]

Do you have any idea?

abi3 builds are considered cross-compiles, so they go through get_platform_tag() in maturin, which already accounts for this:

https://github.com/PyO3/maturin/blob/df427600d13c9b3212c453b093028cef8fad9d30/src/target/mod.rs#L347-L352

The new cp314t wheel goes through a different code path in maturin, which defers to what's in sysconfig to calculate the ABI tags.

[alex]

Ahh, that's teh magic bit. Thanks much!