[clang] [clang-scan-deps] Expand response files before the argument adjuster (PR #89950)

[Jan Svoboda via cfe-commits]

jansvoboda11 wrote:

Hmm, that driver code is only executed if the dependency file was requested on the Clang command line, though. `clang-scan-deps` should be able to generate the dependency file even if the original command line doesn't have `-MD` and friends. That's why we call `deduceDepTarget()` in DependencyScanningWorker.cpp.

In general yes, I'd prefer to solve this wherever we have access to properly parsed command line (or `CompilerInvocation`) and removing the ad-hoc parsing in `clang-scan-deps`.

https://github.com/llvm/llvm-project/pull/89950