Inconsistency between Clippy and Rustdoc build stages

[Aaron1011]

If I run:

./x.py build src/tools/rustdoc --stage 1

Then I get a rustdoc built against my local stage1 compiler

However, if I run:

./x.py build src/tools/clippy --stage 1

Then bootstrap will attempt to build a stage2 compiler, and compile Clippy against it. In order to get the same result as with Rustdoc, I need to use ./x.py build src/tools/clippy --stage 0

As far as I know, both Clippy and Rustdoc are both the same 'kind' of tool (they are a frontend that runs some of the compiler's passes), so --stage N should give the same result with both of them.

[jyn514]

cc https://rust-lang.zulipchat.com/#narrow/stream/122651-general/topic/Idea.20for.20explaining.20stages.20better/near/212184384

[jyn514]

cc https://rust-lang.zulipchat.com/#narrow/stream/326414-t-infra.2Fbootstrap/topic/Stage.20numbering.20for.20tools

[onur-ozkan]

This should no longer happen since #137215 PR.