Rollup merge of #71691 - ecstatic-morse:const-unreachable, r=oli-obk,RalfJung
Rollup merge of #71691 - ecstatic-morse:const-unreachable, r=oli-obk,RalfJung

Allow `Unreachable` terminators unconditionally in const-checking

If we ever actually reach an `Unreachable` terminator while executing, the MIR is ill-formed or the user's program is UB due to something like `unreachable_unchecked`. I don't think we need to forbid these in `qualify_min_const_fn`.

r? @oli-obk

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