Rollup merge of #114415 - Kobzol:bootstrap-check-vendor-gcc, r=ozkanonur

Skip checking of `rustc_codegen_gcc` with vendoring enabled

`rustc_codegen_gcc` currently cannot be vendored, which [breaks](rust-lang/rust#112393) `x.py check` with vendoring enabled. Until the vendoring issue is resolved, it would be nice if `x.py check` could succeed (and just skip `gcc`) with `vendor = true`. With this PR, it does.

Related issue: rust-lang/rust#112393

r? bootstrap

Author: matthiaskrgr