Support multiple targets for checkOnSave (in conjunction with cargo 1.64.0+)
This PR adds support for the ability to pass multiple `--target` flags when using
`cargo` 1.64.0+.
## Questions
I needed to change the type of two configurations options, but I did not plurialize the names to
avoid too much churn, should I ?
## Zulip thread
https://rust-lang.zulipchat.com/#narrow/stream/185405-t-compiler.2Frust-analyzer/topic/Issue.2013282.20.28supporting.20multiple.20targets.20with.201.2E64.2B.29
## Example
To see it working, on a macOS machine:
```sh
$ cd /tmp
$ cargo new cargo-multiple-targets-support-ra-test
$ cd !$
$ mkdir .cargo
$ echo '
[build]
target = [
"aarch64-apple-darwin",
"x86_64-apple-darwin",
]
' > .cargo/config.toml
$ echo '
fn main() {
#[cfg(all(target_arch = "aarch64", target_os = "macos"))]
{
let a = std::fs::read_to_string("/tmp/test-read");
}
#[cfg(all(target_arch = "x86_64", target_os = "macos"))]
{
let a = std::fs::read_to_string("/tmp/test-read");
}
#[cfg(all(target_arch = "x86_64", target_os = "windows"))]
{
let a = std::fs::read_to_string("/tmp/test-read");
}
}
' > src/main.rs
# launch your favorite editor with the version of RA from this PR
#
# You should see warnings under the first two `let a = ...` but not the third
```
## Screen
Helps with #13282
38fa47fd79
