`./x check library --stage 1 --skip-std-check-if-no-download-rustc` builds rustc

[RalfJung]

It seems some (very) recent change broke the --skip-std-check-if-no-download-rustc flag: if I invoke the command ./x check library --stage 1 --skip-std-check-if-no-download-rustc in a checkout where I changed rustc, I would expect that to do nothing. That's kind of the entire point: I do not want an expensive rustc build. But I want a cheap library check if that's possible.

Instead, I see this:

$ ./x check library --stage 1 --skip-std-check-if-no-download-rustc
Building bootstrap
    Finished `dev` profile [unoptimized] target(s) in 0.03s
WARNING: `--skip-std-check-if-no-download-rustc` flag was passed and `rust.download-rustc` is not available. Skipping.
/home/r/src/rust/rustc.2/build/x86_64-unknown-linux-gnu/ci-llvm/bin/llvm-strip does not exist; skipping copy
Building compiler artifacts (stage0 -> stage1, x86_64-unknown-linux-gnu)
   Compiling rustc_span v0.0.0 (/home/r/src/rust/rustc.2/compiler/rustc_span)
   Compiling rustc_llvm v0.0.0 (/home/r/src/rust/rustc.2/compiler/rustc_llvm)
   Compiling rustc_abi v0.0.0 (/home/r/src/rust/rustc.2/compiler/rustc_abi)
   Compiling rustc_ast v0.0.0 (/home/r/src/rust/rustc.2/compiler/rustc_ast)
   Compiling rustc_type_ir v0.0.0 (/home/r/src/rust/rustc.2/compiler/rustc_type_ir)
   Compiling rustc_error_messages v0.0.0 (/home/r/src/rust/rustc.2/compiler/rustc_error_messages)

It even says that it's skipping, but then it doesn't skip.

Cc @Kobzol

[Kobzol]

Hmm, that was most likely #143048. I'll take a look, thanks for the report.