internal: project-model: when using `rust-project.json`, prefer the sysroot-defined rustc over discovery in `$PATH`#15560

bors merged 5 commits intorust-lang:masterrust-lang/rust-analyzer:masterfrom

davidbarsky:davidbarsky/use-sysroot-rustc-to-determine-cfgsdavidbarsky/rust-analyzer:davidbarsky/use-sysroot-rustc-to-determine-cfgsCopy head branch name to clipboard