Fix if-let chains for compilation on rustc v1.85

[trevarj]

if-let chains are unstable until 1.88, so rewrite in a more functional way that
keeps the same logic and allows compilation on earlier rustc versions.

[trevarj]

I think the clippy error regarding is_multiple_of_2 can be safely ignored, since it is also not on older rustc versions.

[bjorn3]

What do you want to use ar_archive_writer for that you need support for older rustc versions? This crate was created to be used as dependency of rustc itself, which is always compiled with a single fixed rustc version.

[trevarj]

@bjorn3

What do you want to use ar_archive_writer for that you need support for older rustc versions?

It is deeply nested in a dependency of a library I want to use.

➜ cargo tree -i ar_archive_writer
ar_archive_writer v0.5.1
└── psm v0.1.29
    └── stacker v0.1.22
        └── teloxide-core v0.13.0
            └── teloxide v0.17.0

This crate was created to be used as dependency of rustc itself, which is always compiled with a single fixed rustc version.

I see. That makes sense.

Not a problem though! You can close this then and I will just [patch] using my fork. Thanks

[bjorn3]

I wasn't aware that psm used ar_archive_writer. Looks like it was added in rust-lang/stacker#128, breaking the stated MSRV of 1.63: rust-lang/stacker#139