[clang][cmake-caches] The `stage2-check-clang` target not recognized when using the `clang/cmake/caches/BOLT-PGO.cmake` cache

Following the guidance on the https://llvm.org/docs/AdvancedBuilds.html#bolt page, I've managed to optimize clang (using BOLT+PGO). Unfortunately, I cannot verify the obtained binary with the usual round of clang tests (`check-clang`) as the `stage2-check-clang` target listed on the same page is not recognized. Neither is `stage2-check-all`. Copying the optimized `clang` binary to the `build/bin` directory (to overwrite the non-optimized binary obtained in previous stages) is not a solution: running usual `check-clang` (or `check-all`) relinks the `clang` binary, effectively restoring the non-optimized one for the time of testing. There must be another way. Is there something that I'm missing here?