[clang] [clang][perf-training] Fix training when path to cmake has spaces in it (PR #162919)

[Aiden Grossman via cfe-commits]

https://github.com/boomanaiden154 approved this pull request.

> I havne't run into this problem with anything else, but then again, cmake is the only executable called from the lit tests when doing the perf training.

LGTM then. We could preemptively fix the other paths, but if there's no way to validate it, then probably best to leave that for later.

https://github.com/llvm/llvm-project/pull/162919