cargo tests seems to not run by default on `./x test --stage 2`

[jieyouxu]

It seems surprising that we don't yet run cargo's tests in CI for hosts by default (as part of ./x test) on stage 2

$ ./x test --dry-run --stage=2 | grep cargo
Building bootstrap
    Finished `dev` profile [unoptimized] target(s) in 0.02s
Documenting stage2 cargo (x86_64-unknown-linux-gnu)
Doc path: /home/joe/repos/rust/build/tmp-dry-run/x86_64-unknown-linux-> gnu/doc/cargo/index.html
Building tool cargo (stage1 -> stage2, x86_64-unknown-linux-gnu)
Build completed successfully in 0:00:00

🤔

Yeah, e.g.

rust/src/ci/github-actions/jobs.yml

Lines 513 to 516 in 642e49b

	# x86_64-msvc-ext is split into multiple jobs to run tests in parallel.
	- name: x86_64-msvc-ext1
	env:
	SCRIPT: python x.py --stage 2 test src/tools/cargotest src/tools/cargo

That seems weird

Originally posted by @jieyouxu in #141656 (comment)

I haven't looked into this yet, opening an issue to track.