[llvm] Reland: "[Exegesis] Add the ability to dry-run the measurement phase (#121991)" (PR #122775)

[Nico Weber via llvm-commits]

nico wrote:

In regular cmake builds too: https://logs.chromium.org/logs/chromium/buildbucket/cr-buildbucket/8725770427201973633/+/u/package_clang/stdout?format=raw

https://github.com/llvm/llvm-project/pull/122775