test `rustc-dev` dist component on CI

[Kobzol]

Recently, the rustc-dev component was broken several times in a row (#138304, #138647).

It would be nice if we had some CI check that would at least run cargo metadata on the extracted rustc-src component.

CC @RalfJung - Would running cargo metadata be enough as a smoke test?

[jieyouxu]

(Related to #136822)

[jieyouxu]

I also don't think this is really compiletest, it probably needs to be its own test suite post-dist doing some basic checks.

[RalfJung]

Would running cargo metadata be enough as a smoke test?

Yes, at least for these two recent issues that would have been enough.
I was about to open an issue asking @rust-lang/infra for what is the best way to test this. :)

[RalfJung]

(Related to #136822)

Maybe let's make this issue here specific for rustc-src, and use the other one to track more potential tests.