[Beta 1.77] Fix bootstrapping from 1.76

[ehuss]

Due to the timing of the revert for stabilization of c_str_literal (#119528 which reverted in 1.76) and trait_upcasting (#120269 which reverted in 1.76), which happened after #119211 (Bump stage0 to 1.76 beta), this resulted in some of the feature attributes not being restored which are needed to be able to bootstrap from 1.76. This restores those features.

This also includes a stage0 bump to the just released stable. This is necessary because stage0 was currently pointing at an old beta which did not contain the reverts.

Fixes #120810

[rustbot]

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[rustbot]

⚠️ Warning ⚠️

• Pull requests are usually filed against the master branch for this repo, but this one is against beta. Please double check that you specified the right target!

[rustbot]

The Miri subtree was changed

cc @rust-lang/miri

[ehuss]

cc @Mark-Simulacrum

[stefson]

Hi, the fix is working for me. Please note, there is an update of stage0.json file mixed in here! :-)

[Mark-Simulacrum]

@bors r+ rollup=never

Makes sense to me.

[bors]

📌 Commit ec15d9d has been approved by Mark-Simulacrum

It is now in the queue for this repository.

[bors]

⌛ Testing commit ec15d9d with merge 3d66104...

[bors]

☀️ Test successful - checks-actions
Approved by: Mark-Simulacrum
Pushing 3d66104 to beta...

[stefson]

thanks everyone