Addition of --keep-going flag breaks analysis on older repos

[vitalytarasov]

Addition of --keep-going flag in v0.3.2037 breaks code analysis on older repos. Analyzer terminates with error:

2024-08-16T17:38:57.220808Z ERROR FetchBuildDataError:
error: the --keep-going flag is unstable, and only available on the nightly channel of Cargo, but this is the stable channel
See https://doc.rust-lang.org/book/appendix-07-nightly-rust.html for more information about Rust release channels.
See rust-lang/cargo#10496 for more information about the --keep-going flag.
rust-analyzer version: 0.3.2070

rustc version: 1.70.0 (set via rust-toolchain file)

editor or extension: VSCode

relevant settings: default settings

workaround: downgrade rust-analyzer to v0.3.2029

[Veykril]

We are aware of this, either upgrade your toolchain or if thats not possible install the rust-analyzer component in your toolchain and point your editor to use that rust-analyzer instead. We cannot reasonably support older rust versions.

[vitalytarasov]

Why not pass the flag conditional of rustc version?

[Veykril]

See #17662 and #17561