Rollup merge of #64502 - RalfJung:miri-toolstate, r=pietroalbini
Rollup merge of #64502 - RalfJung:miri-toolstate, r=pietroalbini

avoid duplicate issues for Miri build failures

Currently, when Miri regressed from test-pass to test-fail, we pen an issue -- and then when it regresses further from test-fail to build-fail, we open a *second* issue.

This changes the logic to avoid the redundant second issue for Miri.

r? @pietroalbini @kennytm

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