Add cmd option to pass Rustc arguments containing spaces

[humenda]

I am trying to pass pre-link-args and link-args to Rustc using Cargo. These dynamic an hence cannot be in the Cargo.toml. Since they contain spaces, I cannot use CARGO_RUSTC_FLAGS. If cargo had an option as --rustc-arg=, it would be possible to pass (multiple) arguments through to Rust, even if some would contain spaces. This could be useful for passing library paths, too.

[ehuss]

cc #6139, another issue about spaces in flags.

[atopia]

The problem of arguments with spaces in CARGO_RUSTC_FLAGS has been addressed with the introduction of CARGO_ENCODED_RUSTFLAGS in #9601 and the viability of the solution confirmed as part of working on rust-lang/rust/pull/85967. Although this issue proposes a command line option, unless @humenda objects I would argue that this issue can be closed.

@rustbot ready

[rustbot]

Error: The feature shortcut is not enabled in this repository.
To enable it add its section in the triagebot.toml in the root of the repository.

Please let @rust-lang/release know if you're having trouble with this bot.

[humenda]

`CARGO_ENCODED_RUSTFLAGS` is the thing that was missing and I have been wanting for quite some time. Thanks for spotting the new feature.

[weihanglo]

Thanks everyone for participating in this issue. Glad the inconvenience has been resolved!

As a result, this is going to be closed. For a more general --rustflags CLI option, you can find recent discussions here rust-lang/rfcs#3310.