Rollup merge of #77776 - jyn514:wrong-way, r=Mark-Simulacrum
Rollup merge of #77776 - jyn514:wrong-way, r=Mark-Simulacrum

 Give an error when running `x.py test --stage 0 src/test/ui`

The error can be overridden with `COMPILETEST_FORCE_STAGE0=1`. In practice I don't know why anyone would do this.

r? @Mark-Simulacrum

Closes https://github.com/rust-lang/rust/issues/77711

aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust