"master" toolchain no longer accepts -Z flags

[matthiaskrgr]

On nightly (rustc 1.50.0-nightly (c919f490b 2020-11-17) I can run
/home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/rustc ./75323.rs -Zsave-analysis which works fine, but this no longer works with the master toolchain (c4f836a); this worked yesterday!
/home/matthias/.rustup/toolchains/master/bin/rustc ./75323.rs -Zsave-analysis

error: the option `Z` is only accepted on the nightly compiler

[matthiaskrgr]

@rustbot modify labels: regression-untriaged

[matthiaskrgr]

Just saw #79159 , could be related

[pietroalbini]

This is definitely #79159, sorry about that.

[Stupremee]

Assigning P-critical as discussed as part of the Prioritization Working Group procedure and removing I-prioritize.

[matthiaskrgr]

Fixed by #79159