I think that the problem is not specifically bound to a Windows install, as I've encountered it under both Windows and Linux. The symptoms are always the same: the compilers are detected correctly but corresponding kits either have no compiler specified or have wrong compiler set, and I'm unable to fix it as they are autodetected kits, so the option to select compiler is unavailable.
The only workaround I've found is to duplicate failed kits and set the compiler in the duplicate. The workaround produces valid kits, but the kit selection becomes quite messy, as almost for each working kit we have a failed one, and I have to always keep in mind which one is which.
An option of selecting a compiler for an autodetected kit manually would solve the issue. If the Qt developers want to keep the idea of "autodetected means set automatically", a possible solution would be to add a "reset to autodetected" button, but for the case when autodetection fails the option of editing kit manually is, IMO, a better solution than creation of a duplicate.
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