[clang] [clang-scan-deps] [P1689] Keep consistent behavior for make dependencies with clang (PR #69551)

[Ben Langmuir via cfe-commits]

https://github.com/benlangmuir commented:

Is the issue with MDC's FileDeps that we are calling `makeAbsoluteAndPreferred` on the paths?  Maybe we could instead move that call into `FullDependencyConsumer`.  Or are there other issues?

The fact we need to add additional `MDC.IsStdModuleP1689Format` checks in this PR to prevent the normal consumer callbacks is not great. This makes MDC aware of implementation details of the specific output format.

https://github.com/llvm/llvm-project/pull/69551