mingw-check job is building the compiler, not just checking

[scottmcm]

Example: https://travis-ci.com/rust-lang/rust/jobs/177017513

1298:   Checking compiler artifacts (x86_64-unknown-linux-gnu -> i686-pc-windows-gnu)
1502:   Building stage0 compiler artifacts (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)

This is costing an extra ~18 minutes of travis time per PR build (maybe more).

cc @kennytm who I talked with on Discord about this

[phansch]

I added this in #57010. Is there some way to avoid building the full compiler for these tests or would it make sense to move this to another job?

[Mark-Simulacrum]

There should be a way -- IIRC we should be building compile test without building the compiler at all (i.e., using the bootstrap compiler).

[mati865]

@scottmcm I believe it's fixed, here is latest mingw-check job: https://travis-ci.com/rust-lang/rust/jobs/194269571

[scottmcm]

Agreed. Thanks, @mati865!