conditional passing of edition for core

[est31]

Since PR rust-lang/rust#138162, the Rust std library and core libraries use edition 2024. The Linux makefile hardcodes edition 2021 however.

Right now, core compiles fine on editions 2021 and 2024, but my PR rust-lang/rust#140966 encountered a build failure of the rust-for-linux CI.

Talked to @nbdd0121 about this. According to them, it should be possible to add conditional compilation dependent on the rust compiler used to compile the kernel. This matches the expectations of the core library the most I'd say: on releases before 1.87.0, the compiler used edition 2021, and on 1.87.0 and later, it uses 2024.

cc @ehuss